I doubt you'll get that level of detail
As has been said above, in many cases the franchise comes with a list of services that they are required to operate, and the bidders return an overall cost or premium for doing so.
Specific services can be subsidised from other sources, so you might find, for example, that a council may offer a subsidy to hire in an additional unit and crew it to extend or improve services beyond the base-line specification. An example was the Severn Beach line, which used to get an hourly service (and only beyond Avonmouth in the peak), and now gets 3 trains every 2 hours, with one train every other hour all day to Severn Beach. But you couldn't say which of those trains were subsidised and which weren't -- the service as a whole received the subsidy, and since the overall service exceeded the franchise commitment, the DfT was fine with it. That's unlike a commercially tendered bus route, where a council has paid for specific journeys.
However, the detail as to which routes lose money out of the overall pot of services operated by a TOC under their franchise commitments is unlikely to ever be made available -- that information is commercially sensitive (if the incumbent's books were open for everyone to see, they could be disadvantaged when the route is put back up for competition), and quite difficult to calculate (accounting for inter-working of routes and so on, if a driver & train spend some of their duty on a loss-making route, and some on a profit-making route, how do you say what portion of the costs were subsidised?)
Accounting for routes in this way, with an absolute "subsidised" / "not subsidised" label also fails to account for the network benefits afforded by the individual routes. So while Whitby to Middlesbrough may fail to make money, its existence will increase rail journeys on the more profitable routes into Middlesbrough, which would otherwise have not been made. So, some people will take the train from York to Whitby because the line exists, which makes even more money for York-Middlesbrough, whereas if the Whitby line didn't exist, passengers from York would just get on the bus or drive. This was one of the main economic criticisms of the Beeching report, because it failed to see the network benefits of the branch lines, and that could have tipped the balance in some of the more "knife edge" decisions taken in the 60s.