One does wonder if the modern TfL will try and turn them into engineering vehicles, or just scrap them and then buy new trains for engineering vehicles at 10 times the price.
Given that a lot of ex-tube stock engineering trains have been scrapped the past few years can't see any real need.
Apart from the track recording unit (L132/666/L133) and the two Central RATs) there is not anything else. The ex D78 RATS are not tube size so don't count.
The MPU project stopped and cars scrapped, the Asset Inspection train project stopped, the tunnel cleaning train project stopped, and increased use of on track plant and road-rail vehicles, and, probably the most important, there are ££££££s for SFA at the moment. Engineers toys are at the bottom of the pile.
So what actual engineering vehicles is anyone else proposing we need ?
I suggest the whole lot will be reduced to scrap, except, as mentioned upthread, Picc. RATs (which seasonally exist already) + 1 car for Acton museum. And any other mug who buys any for use as a greenhouse, or classroom, or other equally non mobile project.
Remember now that a general use engineers train needing to run on more lines than the Picc, will need other lines ATP like CLATP, DTG, TBTC and CBTC. You are talking seven figure sums per train type to do that. Even if the Picc don't get resignalled for decades, to use 73TS as engineers vehicles elsewhere you'd need most if not all of that lot. You soon won't be able to get out of Ruislip at all without CBTC or CLATP. Does tend to limit scope. The Bakerloo no resignalling plans yet, but you can't get an LU engineers train there without entering from the Jubilee, hence needs TBTC; etc. etc for getting to and from all other lines. It all costs £££££££. And there is no realistic need for other engineers vehicles captive to either Piccadilly or Bakerloo.