A peace referendum would most likely pass in Israel, though it might depend on the exact terms of the agreement. Mostly it would be a vote of confidence in the Netanyahu administration. Having a referendum allows the right wing parties to check Netanyahu and prevent him from making any concessions that come referendum time would weaken him as Prime Minister.
It also ties the hands of MKs who would vote against a deal but are unlikely to win. This way they can be outspoken against the peace deal but not shoulder blame if the referendum passes.
Again, for peace talks which were doomed from the start, there's an awful lot of preparation for the possibility of success.