Is it possible to use the old style "simplimatic" track with one of thenew sets using the ez connect track?
By all means. The base on E-Z Track adds 1/4" to the height. All that is necessary is to put a 1/4" thick material under the old track and it will line up with the new track. Atlas makes cork roadbed strips that are 1/4" thick but other alternatives include 1/4" plywood, 1/4" Foamcore http://en.wikipedia.org/wiki/Foamcore (http://en.wikipedia.org/wiki/Foamcore), multiple layers of pasteboard (non-corrugated cardboard,) fiber board, and so forth. The added base can be cut to clear the hook on the E-Z Track, or the hook can be cut off. You can also cut suitable shapes out of 1/4" material to allow you to use standard turnouts, crossings, or crossovers that you may have or might buy. For some parts of your layout, you might even want to use flex track to produce non-standard radius curves. This trick makes E-Z Track far more useful that it might at first seem.
Jim
make sure the code is the same...ie, 83, 100 and I believe there are rail joiners that will make up the difference or there will be a nice little bump there