I think TfL could take over some routes where feasible. The Northern City line would fit quite well for example as well as some of the outer London routes on SWR and Southern.
The problem will be the “where feasible” bit. Just as with Southeastern, it wouldn’t be possible to neatly hive the chosen routes off; the crews and stock will all interwork with other routes that wouldn’t be suitable for transfer, and the whole thing rapidly becomes much too complicated.
Then, as above, what would TfL taking over these routes actually achieve? Probably one for another thread, but it isn’t immediately obvious how GBR will change any of the above vis a vis TfL and the near-London suburban network.
I still think it will make little difference, all labour are proposing is taking over the TOCs, still little incentive to improve services and even less incentive to reduce overcrowding. Infrastructure will be the same as now, it's just political ideology that's driving this.
There's been positives and negatives from privatised TOCs which have been discussed many times, when a well run TOC is running it everything is rosy, badly run everything is dreadful. If there's regional GBR then a well run region will have good performance and other regions will have their problems, pretty much like today.
It does seem ideological, and smacks of “private sector bad, public sector good” dogma.
With either approach, the main difference going forward will be the new “guiding mind” for the industry, so in many ways the Tory version of just changing the existing TOCs into concessions, while still delivering the “guiding mind” via GBR seems a more straight forward version of the same thing, and one where the benefits of the private sector eg the ability of commercial incentives to drive behaviour can be implemented.
The difference with Labour’s approach is bringing the TOCs into public ownership (not just control). So the question is what benefits that additional step brings, and whether those will justify the cost of doing so. It’s not immediately clear that they will; there will be some savings in terms of removal of duplication, as noted above, and TOC profits could be regarded as a cost, but their margins aren’t exactly huge.
It also risks entrenching one of the biggest problems with the current arrangements: namely that operators are being paid whether they run trains or not, and take no revenue risk. Fully nationalising them will remove any ability to introduce commercial incentives eg allowing operators to offer deals to encourage patronage/drive revenues.