If a site is specifically a GMO, it has legacy antennas, so it can't support any 800 MHz services. But that doesn't mean sites can't have RRUs mounted at the BBU cabinets and NV capable antennas (in which case they wouldn't be a GMO). At those sites, all bands should be possible.
As far as I know, you usually only see something like that in places like rooftops or small/stealth sites (like "flagpole" sites) like this one from the in-progress thread:
Almost all of the sites in the city of Fresno are GMRs, like this:
The legacy gear is kept up in the air only long enough to get the new NV hardware plugged in. All 6 RRUs are on the ground, like so:
The county of Fresno (and Clovis, and everywhere else on planet earth) has different standards, apparently, so their sites look like more like this: