A little experimentation from a remote NH Location indicates you are getting an IMAGE [Again, Where are you located when hearing this]
from the MSP 800 TRS, not an actual 700 Mhz signal.
From Concord NH [well away from any Strong MA Signals] I get
794.665625 and at the same time 860.7375 Mhz is active as well.
Both at the same time. Its unlikely that 800/700 both get the same traffic at the same time 100% of the time unless it was an image.
I would guess if you took your 794.6875 and 860.7375
you will get the same broadcasts.
Add 66.071875 +/- a few khz to your 700 Mhz Channels for the image frequency.
I recently purchased a GRE-600, and while having it in a search mode, have come across 794.6875. Sounds like MSP, and it's statewide. I've heard calls from Salisbury,Ma to Oaks Bluff (the cape) on same frequency. I've done a frquency search with nothing comming up. Any ideas??