I agree with Lowerlobe. Remember in a previous SH EBA there was a one off agreement to allow any ex longhaulers a transfer back to LH, if that's what they wanted. The EBA was voted up, and then the company dropped the bombshell that all of those transfers were to be to the Mel base. No one saw that coming. They all assumed that they could return to the base they had come from. Even the union had not considered this fact, no one had. But all that was in writing was 'a transfer back to LH', nothing about bases.
So similarly now, if the agreement only guarantees your position back in SH after 2 years (with nothing in writing about which base), you may very well end up back in a different base.