Not something you will see very often, even as an airport worker. Only seen one so far, on an Air France Barbie Jet (Emb 145). Quite spectacular, looked like they'd fitted afterburners. Fortunately, it was only momentary, and the engine was not shut down as a result.
In practice, I doubt the pushback crew who visually monitor the engine starts from the front of the aircraft would actually stand and watch a hot start as long as the one in the Braathens clip. Or at least I hope they wouldn't.
They usually have a fairly healthy sense of self-preservation.