http://www.youtube.com/watch?v=8nFH2P0kKho if you nade boost around the tentacles this wont be possible, as you need the window to be smashed open by the tentacle. I haven’t checked times on both routes yet, but from the looks of it, nade boosting is faster. Still, if someone can find a way to start the trigger to get the window broken without actually going in that room, or some other shortcut, this can be faster. You can also go into the room to start the trigger, then go back and do the nade jumps.
It’s possible to press the button from the outside, I have a video of it somewhere around here.
Do you really need a video? The tricks so small. :-\
Of course.