Well I'll be...
Check this out, from an email I just received from Maureen Shirkus, the manager of the Red Line:
Dear [my name],
Thank you for your email regarding the proposed weekend diversion on
the Red Line.
Regular Red Line service will operate this weekend.
When the final request had been sent up to put the diversion in place,
it was reviewed and overruled given the expected high volumes of riders
Operations will work in conjunction with our Construction Department to
schedule the diversion for another weekend.
Seat drops were done over the last weekend and we are now in the
process of removing signage that was placed in stations. Our website
will also be updated.
If you have any questions or concerns regarding Red Line service,
please contact me at firstname.lastname@example.org.
Chief, Red Line Operations
Apparently there was, umm, a significant volume of raised voice (I got an email from the Pride organizers thanking me for letting them know (I doubt I was the first, or only, person to do so), and advising they were working on it, prior to receiving this email).
So. Red Line service will be normal this weekend.