The APD 'holiday' proposal isn't specific to MAN. The transport select committee made a recommendation that the govt should consider a APD holiday of 12 months for new routes outside the South East. MAG as you would expect has started to lobby to get the recommendation implemented, but you can imagine the uproar in the neighbouring cities if something was implemented for MAN only !
30. There are complex issues and vested interests to be taken into account in any consideration of the merits of differential rates of Air Passenger Duty. We recommend that the Government carry out an objective analysis of the impacts such a policy might have. On the other hand, we see merit in the concept of an APD holiday and recommend that this be introduced for a 12-month trial period for new services operating out of airports outside the south east. After this time, the DfT should assess the extent to which it has led to the development of new routes. (Paragraph 106)