What happens if there is 50/50 between BU and core and there is a hard fork? Do we now own bitcoin 1.0 and bitcoin 2.0 or do you have to switch your coins to one and hope you made the right choice? I've never been through a hard fork with bitcoins (or any alts tbh).
BU will not activate until it has 75% hashing power. Once activated, the hard fork won't go into affect for some time, allowing miners who have not yet transitioned over to make the change... or be left behind.
The code is designed so that it is possible at 51%.
75% is what the community is currently agreeing to defer to.
So "activating" at 75% is contingent that they do not agree to reduce it later,
for example if only 65% could be reached.