They have not transitioned to the 700Mhz system yet AFAIK. They only started testing it a few weeks ago in STMC. Maybe they are using another VHF channel?
Like MSP, I don't believe these frequencies have repeaters, so you have to have a good lo band antenna and/or be nearby to hear them-if they are still being used.
I believe St Mary is in SHA District 5 - they are on the FiRST database
If you hear nothing, then that suggests either another TG on the STMC system is carrying the traffic, the use of cell phones, or a different VHF channel. I'm not there so it's hard to figure out. I will say that here in Annapolis, the SHA uses FIRST, and I heard traffic on the Annapolis Shop TG, and the District CHART TG. relating to the snow event.