Good question. I don't remember any tester commenting on that but perhaps someone else will. With regard to another type of sign it appears there has been a recent change where FSD beta knows from signs whether it can go right on red or whether a sign restricts that. I believe it was Dirty Tesla that mentioned that in a recent video. If that's true it would bode well for reading school zone time restriction signs.
Dirty Tesla speculated about right on red, but its possible that data came from the map (or both). My guesses are as good or bad as anyone else, but I'm assuming Tesla get data from the map as well as the cameras. From my somewhat outdated knowledge of AI the map data is possibly used as hints to the AI (such as "expect a right on red restriction here" type of thing). And for clarity, I'm not talking the (much confused) idea of an HD map here, just the basic info available from the nav maps.