There is no question if you get to agree--management issues directives --you get to chose to obey or not.
If not, you then may or may not get fired for willful insubordination--NO unemployment comp for that move.
I lean towards obey and smile --its the best choice in town.
You want to be locked up on site--if you are free to wander about town on 30 minute call it may seriously hurt /kill your odds to get paid for standyby time!
You might get a pleasant trip to bank ?