ERTMS and ETCS are going to be implemented over 50 years because that is how long it will be before some of the existing signalling centres need to be replaced. I expect this list that ATOC have put out is based on Network Rail's signalling road map for the replacement of all signalling control into the 12 new control centres (or what ever this years plan is).
ETCS, as planned for UK, needs to be interfaced via computer based interlocking rather than any pre-existing relay or mechanical technology, so apart from areas that are already SSI or similar, it will have to wait until scheduled signalling renewal dates, which are based on condition, though modified to allow a line of route approach for ETCS introduction. The programme is also constrained by national budgets and industry capacity.
ETCS requires not only the infrastructure to be modified but also the trains. If you recall the Cambrian route is a trial installation and in all the reports on it I have seen the big message is "don't modify old trains" as shoehorning the train based equipment into the Class 158s had been extremely difficult and a source of many problems. So one aspect of ATOCs list is the message that trains will need to be able to accommodate the train based equipment in some sort of timescale. In time it will be a factor in train cascades.
SBB probably have more ETCS experience than any other administration, and have formulated a different approach to overcome the similar rolling stock challenges in Switzerland. They have already introduced full level 2 (as proposed for UK) on a number of new and classic main lines. In addition they have proposed a change to the Europe-wide ETCS specs to allow a simpler functionality based on PZB principles, that is overspeed and trainstop protection similar to TPWS and enforced slowdown at a caution. Modern rolling stock will thus be able to run in full level 2 mode on the new lines and use the PZB mode on the classic lines. Older rolling stock will receive a much simpler ETCS modification, based around the same interfaces to brake and traction controls used by the classic protection systems, though they will be unable to run on the full level 2 lines.
The fact that a technical standard for ECTS/ERTMS exists at issue XX.YY does not freeze the technology used to implement it. That will certainly change over the years but as long as the requirements are met it doesn't matter. I don't suppose the train based AWS equipment in use today is the same that was fitted to steam locos in 1954 but it still works to the same requirements.
Quite right! the core of ETCS is concerned with the message formats for track to train transmissions whether over radio, leaky feeder or balise. The future communications medium may be GSM, wi-fi, quantum entanglement or carrier pigeon, but the message purpose and content will be broadly the same!
