I think Homechoice will have filmfour at launch. The have carried other channels that have gone to freeview on the day of launch; itv3, itv4, abc1, more4 (a channel4 channel) often without any mention of them coming.
As for it being competition for their own channels, all I can say is that Sky are carrying it as well as NTL/Telewest. Sky have both subscription and pay-per view channels and NTL/Telewest have their own pay-per view channels too. Not carrying it would make freeview look like an even better option for customers.