I was booked (as mentioned above) from Sheffield to Oxford at 18.24 (the 16.35 Newcastle-Reading). The pdf timetable on XC's website on Thursday evening showed hourly trains from York to Gloucester/Birmingham up until the 18.55 from Sheffield, but nothing from Birmingham to Oxford after 18.04 (and no XC trains south of Reading). I decided to catch the 15.55 from Sheffield* in order to get on the 18.04 from Birmingham, but this was cancelled (the reason given being a train fault rather than lack of crew). My plan B was to catch the 16.54 to Birmingham and travel on Chiltern via Bicester, but then I noticed that the 16.54 was also shown as cancelled, and was just in time to get the 16.18 to London. My ticket was accepted without question on that and at the barrier at Paddington.
However, when changing at Reading to reach my actual destination of Cholsey (I had a separate Oxford-Cholsey ticket) I heard the 20.52 XC train to Bournemouth (19.04 from Birmingham) being announced, and indeed saw it arriving. It appears on RTT as separate Birmingham-Reading and Reading-Bournemouth trains (I haven't checked the Manchester-Birmingham leg), together with a cancelled duplicate 20.52 Reading-Bournemouth and a cancelled 20.52 Reading-Eastleigh empty stock working -- I presume this reflects multiple changes of mind about what was running. The 18.04 ex-Birmingham appears to have been cancelled.
My initial interpretation of RTT was that the 16.54 from Sheffield had also been reinstated as far as Birmingham, but then I realised that the one that did run was empty stock. It appears that the 17.54 Sheffield-Birmingham was also cancelled, but the 18.55 (17.41 from York) did run, presumably with multiple trainloads of very delayed passengers.
It seems from this that although the published timetable for the 'strike' days presumably reflects what they expect to run, what actually runs may be less than that, or occasionally more.
*Not as inconvenient for me as it looks, as my only reason for leaving Sheffield as late as 18.24 was the availability of a cheap first class Advance on that train but not earlier ones.