That's never been announced. TNSE is a privately held company and doesn't need to announce who owns what.
Personally I suspect that Thomson is the majority but silent owner, while Chipman is the minority owner who is active in running the team - but that's only an educated guess on my part.
The one piece of info someone did point me to: if you look at TNSE's Board of Directors you'll find 3 are associated with Osmington (Thomson), 2 associated with Chipman (Megill Stephenson), with 1 seemingly independent director (CEO of New Flyer Industries). Which suggests Thomson has a majority stake.