It seems apparent to me that Apple leaked this information to US press in an attempt to get the UK to back off. Wouldn't Apple also try to subvert the attempt for US intelligence to get a backdoor? Or do we think Apple has less of a leg to stand on with US and would be more likely to roll over?

Don’t you think out of the thousands of Apple employees that someone would leak it?

Yes “collude” contains exactly the right connotations. Slimy, sneaky, against the interests of the public.