As Hexbear's resident train nerd, this tech actually does exist to my knowledge. Japan uses it extensively, which makes sense considering their very busy railways with frequent railroad crossings. Japanese railways use obstruction detectors like these (the little tubes):

If the crossing is clear this sign lights up, letting the train driver know it is safe to continue. I believe if you intentionally disrupt the crossing you can be fined. This information may not be entirely accurate but it appears to be the case.

Here's a video on how crossings work in Japan.

Other things to point out:

-There are extensive grade crossings along the Brightline route and FDOT is absolutely car brained to the point of sheer lunacy, making grade separation something that should absolutely happen on this corridor

-None of this excuses the foolish actions of the fire truck driver