Given that Concorde's sonic boom reached the ground, it also must have reached other nearby air traffic.
How was this dealt with? I imagine passengers would not welcome hearing a loud boom during their flight.
According to this airliners.net post (written when the Concorde was still flying, BTW), the Concorde's sonic booms could often be heard from other aircraft, but never posed problems for said other aircraft:
Sometimes, to the South of Ireland, during the early part of the acceleration on a Westbound flight, Concorde flies over subsonic traffic that is arriving from the USA and cruising around FL370-FL410. If close to this traffic, by which I mean 10-15 miles, then ATC will often warn them that they may be "boomed" as the shock waves pass over them.
From the reports I've heard from some of these crew, this can vary from nothing to a clearly audible double boom, but nothing to cause any concern or alarm.