In terms of timing / stock allocation and crew allocation, sure the Short Term Plan would have been cancelled and in most cases reverted to the Long Term Plan. That happened on the night 'er Maj carked it and the RMT pulled their strikes scheduled for the week of mourning.
However actual individual humans have to be rostered a minimum of 4-5 days in advance (bearing in mind that in some circumstances it can be up to 2 hours before/after their original book on time) which is then pretty much set in stone, mostly so that rosters/resources can then move on to sorting out the next tranche of work but also so that traincrew can plan their lives. If things change in a shorter period of time than that then there is no obligation on traincrew to change their plans unless they are agreeable to doing so; or if they are "spare", there is no obligation for them to come in earlier or later than rostered. Most folk will gladly change their plans if it benefits them and/or an incentive is provided.