I'm not sure if the Fireground frequencies have been in use for a while, but they are programmed in multiple agencies radios (HP, Edison, Metuchen) that provide mutual aid to New Brunswick. I do know that New Brunswick Fire have said in the past to switch to Fireground, and then nothing was heard on the NJICS talkgroups for a while until they needed to communicate back to dispatch, and then that was on the NJICS. I've been trying to hunt down these fireground frequencies for a while now, and finally was able to get them within the last week.
Now, I will say that there is a possibility that the frequencies I submitted might be in a 6.25 kHz step, instead of the 12.5k step listed in the database. I used signal stalker to find them, so they might be a slight bit off in frequency. But the listed frequencies should be enough to monitor them if you are close by. I tried to do a search through the FCC licensing system with the listed frequencies, but nothing was found on them. Perhaps they are licensed as low power 700 analog frequencies by the State under some sort of blanket license that they have (similar to Newark's 700 FG frequencies)?