In both systems, the portable radio uses different NACs to "steer" the extender to different mobile channels (i.e. Ch 1 car-to-station, or Ch 2 car-to-car on the base frequency). The "alternate" VRS freq ended up being used as the EV-20 freq for each area.
I believe the portables are programmed for F7E (open NAC) receive on the EV-20 system, so maybe listing the EV-20 freqs with no tone in the DB is the right thing to do in any case. I'm just confused...EE6 everywhere, and then of course I come across EE4.