It is definitely cheaper. O gauge FasTrack Sensor tracks are $95 each. I bought 3 to cut up to make 3 S gauge Sensor tracks. The IRV2 is 2 Sensor tracks for $100, and for $30 2 more can be added, 4 for $130.
The sensor and programming package looks like it will just drop in between the ties and rails of Gilbert track. Using scale track or MTH flex track the sensor will still have to be separated from the programming module. That requires some cable and connector fab and fit up.