All I can speak from is experience. If I am working on a live fault and it requires a TPM/'Lift & Shift' .......... then it is done in the here and now.
I will ring the owning ISP and they will either agree or disagree with my request.
If they agree (which they do 99% of the time), then they will seek a new DSL port on their equipment in the particular Exchange I am working in, and then perform the 'Lift & Shift' ............... it is at this point the downtime begins, and is only exacerbated by the physical time is takes to re-run the connecting wire to the new port on the Main Distribution Frame (MDF) in the Exchange.
Even on a large split-building scenario like Wigan have, this is 90mins at the most. Average probably about 30mins ??.
I can only assume Rev is talking about a pre-ordered TPM ?? By that I mean the service provider booking a slot for a 'Frames (MDF) Engineer' to re-run the wires to the new port that they themselves have allocated. Unfortunately, they are unlikely to get a next-day service as all our work is pre-planned. If I were him, I'd be tempted to ask what date the physical TPM would be carried out by the Frames Engineer, and then have his guys remotely switch the ports on that day, thus keeping downtime to a minimum.
Alas, I don't know what goes on behind the scenes, I just know how long it takes to do the physical side of the work, on average.