Regret unlikely to see many engineering trains on this one, Rod, it's more suited to R/R machines and road deliveries via Dawlish station to the main site, which is quite close.
I've been out there all day, and since getting home, have had to deal with the outstanding work-related stuff first, of course. It's taken a fair few minutes to get this far in this thread, as well.
As Rod and one or two others have said, it's pretty meaningless to start bandying timescales around at the moment, certainly until the next few days of subsequent storms have been and gone. Fortunately, I think the wind is backing to the south-west and west, now, which will be much less damaging than last nights south/south-easterlies (the worst possible wind direction for the sea wall).
A clearer picture will emerge in a couple of days, regarding timescales for repair, so we should wait for that. Bear in mind that you can't work in a location like that most high tides, so that's a large chunk of every 24 hour period effectively 'out of bounds'. However, the 4 - 6 weeks would, all other things being equal, be achievable.
The original foundations are still extant, so we will build new concrete sub-structures on that, building it up until we've got replacement structural support in place. We are mobilising contractors right now and getting manpower and materials, machines etc. marshalled. The repair being currently planned should see the wall looking in outward appearance as it did, before the breach, albeit with greater 'hidden' structural integrity.
I recall the last major breach, which was January 1996, when Sprey Point again got damaged, plus lesser damage in the Rockstone area. The railway was reopened within 2 weeks, IIRC. This one is much, much worse, and is the worst damage I've seen in my 21 years in the SW.
There will also be a longer term plan, already in existence prior to this event.
Most of you will know my views on diversionary routes - 'pie in the sky'. Major expenditure required on Meldon Viaduct, plus one other viaduct, to enable them to take modern trains at sensible speeds. You'd have to reverse twice between London and Cornwall, the reversal between St Budeaux and Plymouth North Road being particularly time-consuming. I personally think that Bere Alston - Tavistock will happen, but it will be a single track line, that may have to share some of the line of route with a cycleway.
The political fall-out from not serving the major towns in South Devon on the main rail link would be too great, so the 'Southern' route loses out in that regard as well.
I feel desperately sorry for the family who's house was partially falling into the sea in front of my eyes, earlier this morning. Areas of tarmac of what used to be Sea Lawn Terrace also fell into the void. Fortunately, all present were sensible enough to keep well away from the edge! The press were kept further back, beind a Police line.
I've got loads of photos, but frankly, I'm just too knackered to post much else now!