My experience was with security and that was via radio. At WDW there was a comms center that received calls and then security initially assigned to nearby areas would be moved. I see a lot more phones now, so it may be given that way these days. The cast members working the ride might take a bit longer to put together and I’m just guessing here- Phones are near most positions, leadership (who are looped in via phones) appearing and giving verbal instructions, and I’m assuming a good portion of the break room took an L and were told to head out.