Staff travel isn't taxable as it does not cost the employer anything to supply
Yes of course there are some costs, Admin. alone, tho' with the move to more computerised ticketing that might be only a few bytes on a computer now.
I accept that I am probably one of only a few in this respect - but as BA don't even fly to NZ I usually cost them nothing but a possible Admin. charge as above, the airlines in the Interline agreements carry me, but I need to remain in the Staff Travel 'family' to be able to use them.
When Doomsday finally catches up with me in 2014 I will see retired staff from other airlines flying in seats on 'my' airline - whilst I'm denied the right to reciprocate on 'their' airline. ( I mainly use Qantas AKL - LAX v.v )
As a dying group, the Old Buffers being thrown out would hardly be a blip on the B.A. radar.