There are exceptions, but they are clearly announced.
I've waited in a "ground hold" for as long as a couple of hours. We pushed back from the gate (so they could use the gate for other flights), then parked on a taxiway near the runway. The captain announced his plan, and everyone was allowed to use cellphones, laptops, etc. until we were cleared for departure.
The destination airport was backed up due to weather. The FAA instituted the procedure back in the 80's to avoid wasting fuel in a holding pattern.
With the new rules about delays, I don't know if the airlines do this any longer. There's a risk of getting fined, so they may just cancel the flight instead.
There are more details to the story from TMZ