I was sitting long call on TDY in Denver this summer. I went to the Natural History Museum they have there. Turns out there is no cell reception in the building. So when I leave my phone chimes a voice mail. I call scheduling and said that I see I just got an assignment. She says, oh yeah! I called you four hours ago. I'll show you notified, have a nice day!

Point is I guess, they didn't really seem to care. Wouldn't recommend doing it on purpose, and YMMV, but you know, that's that.