700 meters or so is the recommended minimum altitude to open a parachute, but of course you can open it much lower and still survive.
Anyway opening a parachute while falling down gives you no guarantees, since you have to do it in a precise way to avoid getting tangled with the tower.
I used to be a skydiver, but it became to expensive to fast
i heard a base jumpers have opened parachute at height less than 400 meters and they still have more room for error (i saw a video once). but i think the 700m recommended is for very high jumping such as skydiver (tens of thousand feet of drop) where you have build up a very fast free fall speed at 700m. just my 2cnt, i never/havent do skydive.
being getting tangled, is one of the more likely problem. but it can still provide option for quick way down. o well, i was just giving a crazy idea, the chute may as well annoy the climber just as the strap does
since looking at the video is very spooky esp on the very top of the antenna tower where you just stand on a very small base with no really hard metal to hold on, i can see just a small metal "pipe", but i think that one is like going to break. and there are two guys climbing it and the one is maintaining the first person's bag, IIRC. if one is going down, i think the other one will be, too.