Run New Polar Express Remote on old 3-rail track

If you have a transformer already, you don't need the track connection for this locomotive, it uses the 18 volts on the track from your TMCC, Legacy, or DCS power supply.  The brick has nothing to do with the remote control, it's just a low power supply for the train if you have nothing else.

No need to use the power pack or FasTrack. I assume with TMCC & Legacy that you have fixed voltage on your track already. The train will run on it. It is capable of running on the 18v DC power pack supplied or 18v AC. You can only control it with the remote that it came with. It will not interfere with the other trains.

Put batteries in the remote, place the engine on the track, turn on the track power as you usually do, operate the remote. The tender and cars work fine on 18v AC also.