The Avanti contract included FS/Trenitalia to provide high-speed expertise for planning HS2 services.
Presumably there will still be a need for GBR to need advice on HS2 operation, and Trenitalia is an obvious contender (as a consultant).
Yet another conundrum for the GBR creators.
Of course, the HS2 scope and timescale has changed completely since the Avanti contract was signed.
The HS2 trains are supposed to be derived from the Frecciarossa 1000 used in Italy/France/Spain, so another reason to involve Trenitalia.