LHR are using baggage express at the moment. They delivered a bag to me yesterday afternoon. BA did an excellent job of losing my bag on the outbound and inbound trips of my CE LHR to BCN trip last week.
Are you sure it wasn't Express Baggage? If so, they are Menzies - who bought out Pony Express some years back and therefore inhertied the BA contract.
You can test if they are involved by entering your BA reference
here