Don't get your apples and oranges mixed up - you're going to end up with mush :.>>
Rebanding has nothing to do with the new 700 mhz system (not 800) nor does it have anything to do with the Baltimore county P25 system. We have a separate thread for that, by the way. In addition the 2096 can be rebanded, but that's quite OT for this discussion...
As you correctly implied, multipath issues are a big problem with this new LSM modulation that these newer systems (such as Baltimore city and Baltimore county) are using. The Unidens don't do very well with this. It would appear that the RS/GRE models have more (although not complete) success with it. Whether the new 700 mhz system will be using LSM is anyone's guess at this point - I don't think that has been decided yet, although I could be wrong about that. I don't even know if they will be using Phase II which no scanner can handle at all (The PSR800 can handle the beta flavor of this scheme..)
I suspect that what will happen is that MSP will use the 700 mhz system when they can, and if they have coverage issues, will revert back to 39mhz. That is the pattern they use when they are using a county trunk - for example, on the Upper Eastern Shore Consortium system. So I wouldn't prepare to drop any 39 mhz programming just yet.
Mike