It is possible, but indeed it is going to take a bit of work. Let's take a glance at what is going to be needed to have your brick fireplace restored to how it looked before it was painted over.
A 'masonry paint stripper' is going to be required which is made for bricks specifically. There are options on the market that are going to be better for concrete, but you are not going to need that particular option. Be attentive to the option you are going with in this regard . Make sure to test what you are doing with regards to the paint stripper to see how the brick reacts. Don't go all in at once or you might make things worse.
Make sure to spread the paint stripper as directed on the bottle. When it comes to cleaning the paint off, make sure you are doing it with the help of rags and warm water. It will do a more comprehensive job with regards to the final result.
Paying attention to the room's temperature is key as well. If the room is going to be 'below' room temperature in the next 30 days (after the process is completed), you are going to ruin the brick and its condition. Make sure it is done in the warmer months to avoid this problem at all (2).