'James Comey went as far as to describe encrypted communications as "something expressly to allow people to place themselves above the law."'
Perhaps the companies being discussed would care to sue the FBI for slander? They've got the legal muscle from the patent wars, and this could be a rare case where public opinion would be likely to be behind the corporate monoliths. If they did get a backdown from the G-Men, it would send a strong message to the politicians determined to go down this road.
As an aside, shouldn't Cameron be sucking up to the corporate monoliths and their big coffers in an election year?* It's not like the oil companies or banks are going to have a lot of funds in 2015, I'm surprised he's still going after the internet mob.
*In terms of typical behaviour, not the right thing to do