I can only comment on what we did on UK Mil SAR - I don't know what limits are in the Bristow Ops manual - but as luckyrat says, if you could see the surface you were legal and on SAR didn't actually have to be clear of cloud. It had to be justified though - normally lifesaving.
HEMS will have higher minima but again, those will be in their ops manual.
I have operated in mountainous terrain day and night in crap weather and it isn't a place to be if you don't know what you are doing and don't have a really good reason to be there.
The pilot in the video didn't really have a clue and should have found a different route - at least he survived to learn the lesson, plenty don't.