Yes, it's very possible, and in fact, it's quite commonly done in commercial FM broadcasting, in order to provide full coverage for major metropolitan areas.
The key to making it work is to make sure that the modulation (not the carrier) of two transmitters is time-aligned in the "overlap" region where the signal levels are approximately equal (e.g., within 6 dB). Outside this region, an FM receiver will "capture" one transmitter or the other, but inside this region, it will randomly jump from one to the other. But as long as the modulation is time-aligned, the output of the detector is essentially the same regardless.
That isn't to say that there aren't many compromises in such a system. Given the variabilities of terrain, etc., it's impossible to get optimal time alignment in all of the overlap regions. Considerable effort goes into modeling the placement of the transmitters (and to some extent, adjusting their power levels) in order to position the less-well-optimized regions away from high-traffic areas.
In the distant past (1990s), I worked for a company that sold networking equipment to commercial radio stations, and I designed the part that implemented the required timing control.