We've gone off the thread a little here, but at least in Europe you are told the length of the delay and given a slot time. The standard response to a start clearance in China is "Standby". After further questioning the next response is "No time" which means length of delay is unknown.
After further questioning the standard response is "Military" or the blame is passed on to the next sector.
The longest delay I've had is 3hrs40mins, it's difficult explaining to Pax that we've no idea when we will be under way!
Fx