Live 8 concerts were held on July 2nd, 2005.
On that very day Mark played in Montreal, Canada, for the North America Leg of his acclaimed Shangri-La tour.
No doubt that the venues are booked way in advance, but i'm quite sure that Live 8 was also prepared way in advance.
I find it a pity indeed that Mark could not accomodate that. Dire Straits had done it for Live Aid in 1985.
When you see proceeds generated by the 23-minute Pink Floyd reunion... you can dream that a Dire Straits reunion would have had as big an impact ! (Even tough MK and John Ilsley never fought to death like David Gilmour and Roger Waters did, hence making the reunion less incredible
).