I have a load of old M-track material and I want to use it to create a shunting yard attached to my new C-track digital layout.
I'll have a spur from the C-track section to a C/M transition rail and thereafter an all M-track section. The digital locos, controlled by the MS2, will run throughout the whole system whether on C or M track.
The M-track turnouts, uncoupler rails, etc. do not have decoders so I will power them from an old 6611 16V AC output lighting transformer and control them through the old blue switch boxes with red/green buttons used for 5202 turnouts.
Does this sound OK? In particular the powering and control of the M-track turnouts etc?

I agree, you could use K83 or M83 decoders for your M track switches. I have played around with mine with K83 decoders and had no problems at all
Finding used K83 decoders on eBay isn't terribly hard, I picked up a few for about $25 each and of course each K83 will operate four switches, so its not a bad deal

The Viessmann 5211 is equivalent to the K83 and has an added advantage that it can use external power for the solenoid powering rather than the valuable digital power. There are other manufacturers as well such as LDT and MAD4. I use all 4 types depending on when I can get a good price on one or the other.

Peter