To answer your question you need to have a bit of background.
Flying in the UK/Europe is more expansive than in the US and Canada, for example, we pay an average of 82p+17.5% VAT for every litre of 100LL (~ $1.40 per litre or $5.30 per gl.). In the States you can fly a twin for ~ $130, in the UK you pay (for the same Seneca) near the $300. These price differentials motivate many people to go to the USA to obtain their licence/ratings.
There are two UK schools (that I know of) that own a subsidiary in the US. Some schools in the US have ‘agents’ in the UK who acts as a contact point.
From the explanation above, you can understand why UK schools want to have the subsidiaries, they catch some of the ‘run away’ cross Atlantic business. It also explains why it is unlikely for them to co-operate with a US school, they will be the loosers. Saying that, at the end of they day it is down to the agreement Saying that, it is down to the agreement and the nity gritty.