It’s easy to predict. If there is a 269-269 one of the Republican electors will be bribed or blackmailed into voting for Hillary.
Unfortunately there are plenty of “Never Trumpers” in the house and senate. It would definitely be close and lots of palm greasing going on. The key would be to do the vote FAST, and not allowing enough time to turn into a complete corruption circus. Guess that’s why the 12th Amendment specifically states “immediate” vote.