I admit that link is rather long and I didn't read the whole thing, but I see a lot of real-time exchange of
data, but the only voltage/reactive power control part I spotted was Article 22 1(c), which doesn't clearly say anything about
real-time control.
And the original long PDF, page 21, mentions the use of Operating Procedure 7.4 Dynamic Voltage Control, and it very vaguely mentions programming of the RRTT (which seems to include the 7.4 schedule) the day before the failure and the day of the failure, but I didn't see anything about the operator programming the RRTT during the failure to control voltage.
It seems to be (and this is not any sort of control theory analysis) that, if the grid voltage is too high (in specified range, but high enough that tap changers must operate to avoid disconnecting generators) and additional reactive power absorption is needed, then the grid ought to react by operating the tap changers (because it's necessary) and by somehow instructing the generators to absorb additional power despite the operation of the tap changers. And I see plenty of discussion about the tap changers in the big PDF as well as plenty of discussion of data acquired via SCADA links, but I don't see anything about adjusting the reactive power schedules to compensate for the operation of the tap changers or about the use of any sort of real-time SCADA control to adjust reactive power.