Everywhere I look for these models I see they are on 'Advance Reservation' status.  Did any make it to North America yet?  I can't find pics online of either a prototype or a model, except the model pix on Bachman's website.  Looks like they haven't gotten here yet, so no one has seen one.  I see Bachman is offering a single car in MBTA paint or in 3 or 4 unlettered paint schemes,the only difference being the stripes.  Looks like there is only 1 type of car. Can't tell whether it has a cab.
The Nanjing Puzhen Rolling Stock Works made bi-level commuter cars but I don't know if that is the prototype.
Both N&W's J-class and SP's Daylight locos had air horns.  It wasn't that unusual to find steam with air horns.

IIRC they are models of Chinese cars

Thanks

Are there any retailers in the USA who stock the Bachmann Branchline line of OO scale models?

One might try 'Great Decals' www.greatdecals.com

Diesels dont require as much of a major facilty as steam.  On the Seminole Gulf in Florida., one guy drives a fork lift and lifts a pallet of sandbox play sand in bags up in the air.  A second guy opens the bags and pours the sand into the diesel's sand fillers.  A local fuel company's tank truck comes around every Tuesday morning and refuels the locos wherever they are parked.
Steam locos required a more extensive facility.  While the facilities seem elaborate to us today they were commonplace at the time.  They were the price of doing business.  First you need water.  If the loco runs out of fuel the fire goes out.  But if it runs out of water, the boiler explodes.  You need a water tank at each loco terminal, at each town and at the bottom and top of every significant hill along the line. 
Then you need an ash pit.  A steam loco's range was determined by the size of it's ashpan.  The pit could be elaborate like the Walthers model or it could have just been a pit between the rails but it had to be there. 
Coal may have been loaded from a coal bunker, or using a steam shovel, or a hoist.
The ET&WNC used a conveyor, the Gainesville Midland had a loading dock at tender deck height and used large wheelbarrows to load coal.  The entire train crew joined in the coal loading operation.  They placed a couple of wooden planks across to the loco's sand box and carried sand to it in buckets.
If your steamers burn oil you can do away with the ashpit and coal bunker and just pump oil out of a tank.
There was once a steam loco that operated around here, that was built in the early 1900's.  It went from a coal burner, to oil, to coal, and ended its days in 1942 burning wood.
You also need somplace with an inspection pit, for inspection, lubrication, and repair of the running gear.
These facilities were neccesary to the operation of a steam locomotive.

Like everyone else I grew up on Athearn kits.  Over the decades I have accumulated three closets full of 'stuff'.  I can re-equip my layout with models of several different eras...the local modern shortline; 1960's; 1940's; but basically my interest is in the 1920's, and Athearn made no freight cars that interest me. 
Going to the hobby shop, getting a BB kit, trucks, couplers, details, paint and decals, then building the car, was a hobby in itself.  I miss doing it.  The process was a stepping stone in the growth of new modelers, ensuring the future growth of the hobby. 
I could care less about the future of the hobby;  I got mine, I don't need yours.  But one would think the manufacturers WOULD care.  It just seems like Horizon, Kalmbach et al are slitting their own throats.  They won't see any more of my $$.

I had a similar problem years ago and they sold me a set of drive wheels with rods attached.  They may not have parts anymore.  Be sure to re-align everything when re-assembling, or it will happen again.   Try contacting North West Short Line to see if they have a replacement gear.  The ten-wheelers have wheels that are keyed to the axles; they can not be reassembled out of quarter.  Dunno about the drives on the 2-8-0s

The Precision Scale cabbage stack is meant for a small shay and is too small for the 4-6-0.

My local logging railroad used onion-stacked 4-6-0s, 2-6-2s, 4-4-0s and a 2-4-0 until 1944.  The 4-4-0 was built to burn coal; converted to oil; re-converted to coal and ended its days in 1942, burning wood.  There is no appropriate onion stack in HO;  the one brass casting is meant for a small shay and is too small.

It must have been REAL easy to spin the wheels on that thing...

What the hobby really needs is a model of the Camden & Amboy's Crampton, and Monster.  They would be the perfect complements to Bachmann's John Bull.
Hey, B-man, how about it?  You already make the tender...

There are two 4-6-0s and three tenders.  I own locos with all 3 tenders.

The headlights, generators, air compressors, check valves, injectors etc. were 'appliances' and not part of the basic locomotive, therefore specified by each railroad.  The use of similar appliances is what gives your loco's a 'family' look.
In the olden days, headlights were sometimes covered by sheet metal, as noted above, to protect the light.  The metal cover was removed at night.  It was simple to remove a non-electric headlight to protect it when it was not in use.  Remember, daytime headlight use was not popular until after WW2.
Steam locos did not carry ditch lights.  They originated in Canada in the 1970s.

I use high level stands for the mainline turnouts and ground thows for the industrial spurs.  The targets are painted green facing the operator to indicate the switch is in the 'normal' position, and yellow to show it is reversed.  The ground throws have the handles painted in the same way.