A picture would help in offering suggestions. When you say there are bolts, do you mean there are bolts holding the plaque in place? If so, then just removing the bolts by unscrewing them may be all you need to do. Why do you think the bolts are glued in the mortar vs screwed into an anchor?

If you use a pry bar you will most likely end up damaging the brick.

Bad choice of words, but they are not bolts that can be screwed on or off.

Not at home to take a pic of our actual address plaque, but here's a visual. Also here is a link to a youtube video showing how it's installed. Holes are drilled into the mortar, holes are filled with glue, and then the plaque is pushed into them to secure.

https://www.youtube.com/watch?v=K8rjUA6tGCY

I would contact a company that manufactures the plaques and ask for advice on how to remove. I wonder if you could heat them from the front and soften the glue enough to pull it off? Probably something hotter than a hair dryer, less dangerous than a blow torch? Maybe an iron?

I wouldn't use a pry bar unless you want the bricks to come down. This is not a time for brute force. Unless you want a much bigger project (potentially residing the house because you can't match the brick). Before you start anything, make sure you cannot unscrew the bolt. The "glue" could be anything from a silicone or other caulk to gorilla glue or epoxy. Can you get a blade behind the plaque?

If the plaque is recessed into the brick, then this could be one of those times where you have to work with what's there and replace the light with something that doesn't require the plaque be removed. Even if you are able to remove the plaque, what will you do with the open/recessed area that's left showing below the new light (I assume the new light won't cover the whole area)? Also, the newly exposed area behind the plaque may not be nice and clean, plus you'll have two holes with adhesive that now have to be dealt with.

I just watched the video and see where they recommend epoxy for installation. That doesn't mean the installer used epoxy but after seeing the length of those rods I don't think they'll be coming out easily.

If you ever decide to install another plaque, I would suggest using one that is bolted on. I understand glueing one in place prevents theft, but I'd rather replace one than have to deal with with trying to remove one that's permanently installed. Both of my plaques are bolted onto brick and I've never had a problem with theft nor do I ever notice the bolts.

did you ever remove the plaque