This is a UK wide tax, not specific to LHR/LGW -- though in practice 99%+ of pax affected are leaving from LHR or LGW. It also applies to MAN and GLA, for example. Maybe the reason that AA discontinued this benefit of paying the tax on our behalf is because the pax were not perceiving that it was a benefit and thankful for AA to do this. Probably the original reason was the processing the tax was expensive and AA chose to absorb the cost. As for those who haven't been charged yet for their e-vip upgrade, you will be when you board. Or at least that is what I have been told (basically the GBP20 is charged at ticketing time if the upgrade clears prior to ticket issue, otherwise it is charged when you fly).