They bugged every single new car going into Northern Ireland? I guess the British are willing to infringe on pretty much anyone's privacy in order to catch terrorists.
Indeed, though I can't believe they had the resources to bug every single car, let alone listen to the transmissions, assuming keyword recognition or similar wasn't about.
They didn't need to listen to all transmissions. They knew which cars they wanted to listen to. Their problem was how to bug them, because presumably cars were bought through a 3rd party and with immediate, on a spot delivery.
See, this is what the US needs: a secret service that doesn't destroy people's privacy or break in in the middle of the night but actually gets its job done.