Preference would be to chuck the phone altogether (at times), but yes there are times when being able to continue on a business call is necessary / helpful and the incidence of protracted waits (one good one last week was 2 1/4 hours!) on the tarmac make the policy bothersome. For example, BA, CX and SQ to name a few, allow phone use up to the door closing, whilst IB for example won't.
Back to the question: answers anyone?