I suppose if nobody says anything, nobody knows anybody is there, so there's no risk of a collision, until of course the windscreen fills, then you'd better be the first to transmit. I suggest you lot look at AIP ENR 1.1 page 47.
Bloggsy:
I agree with your point, but the AIP only says that "good airmanship dictates that pilots of radio-equipped aircraft would also monitor the radio and broadcast their intentions in accordance with the minimum calls...". Nevertheless, such calls are not MANDATORY according to CAR166C, unless there is a risk of a collision.