I'm not sure how an EU regulator could collect any fine from TFL. If the EU regulators go after EPC's EU entities, it might be that TFL would indemnify EPC, but if it doesn't then that would seem to be the end of the matter.
The real problem is that if the data-sharing arrangements have been abused, the EU could simply cut-off the UK's access altogether (the trade and cooperation agreement has provisions for that), which would have serious adverse consequences for the police.