It is a somewhat murky question. The TCA (negotiated and signed by the UK and the EU) allows for UK airlines to wet lease in aircraft from EU carriers, wet lease does include the aircraft and the crew to operate it (ACMI, Aircraft, Crew, Maintenance, Insurance). EU airlines cannot do the same from UK carriers under normal circumstances, there is only a provision for special circumstances which in every single case is subject to in depth review and approval from the local EU authority. The TCA, as negotiated and signed by both sides is not about a level playing field in that regard, it is deliberately written for unequal access to each others markets.