Probably a situation where Freightliner hasn’t been able to resource one of their locos or drivers for it, and Colas has been called to step in. It happens surprisingly often, a few years ago it was reported that when certain Aggregates contracts were up for renewal, DB bought out the company train for a “woo-ing” type trip to the West Country. Passing Exeter Yard, DB were quite keen to point out one of their trains operated on behalf of said company, until they saw a Colas loco on it (another subcontracted service).
Oops.