I've definitely seen pics in a guide thread where someone changed a beam without disconnecting the brake lines, it wasn't on here, think it may've been 205 owners or something, but was a 306 beam I'm sure. Simon (C2K) told me about it I think. Can't find the thread now though so doubting myself! 
If it turns out you need to remove them, make sure you get some penetrating fluid on the bleed nipples asap, will be frustrating if you get everything done then snap a nipple off trying to bleed it!!
If it turns out you need to remove them, make sure you get some penetrating fluid on the bleed nipples asap, will be frustrating if you get everything done then snap a nipple off trying to bleed it!!