I saw an 85X Special at Bayshore Station recently as well, but it still seemed to have Gatineau as the destination, at least on the GPS feed. Not sure why they exist, though. Might be used as an extra or when the final destination isn't known to the operator for that trip? I mean an 85 Gatineau ends at Terrasses, but an 85X might signify it might end before or at Terrasses?
Back in the day, they used the X routes to tell passengers the trip was a special branch of a route (i.e.: 97X South Keys vs 97 Airport, 97X Nepean N vs 97 Bayshore vs 97X Tunney's Pasture, etc.). Though, after the service changes in 2011 I recall the X signage to become rarer (i.e.: 97X South Keys was just the 97 South Keys).
I have seen on a couple occasions, though, buses signed up as simply X Special... that is a very mysterious route...
That was being built while I was a student at Algonquin, which was between 2010 and 2015. I still remember the 118 (now route 88) having to basically loop around the old station to continue west on Baseline, sometimes at speeds... good times.
At the time, the roadway between Baseline Stn and Constellation Cres wasn't built, and Constellation Cres was a literal crescent, joining to Centrepointe Dr at both ends (the southern end of the old crescent is now Gemini Way, as Constellation now ends at Baseline Rd and connects Baseline Rd to the Transitway).
I also remember the 118 not getting many articulated buses, but mostly Orion VI and New Flyer D40i buses instead, as the city used what D60LFs they had on the 95 and 97. That changed when they received the D60LFRs and started retiring the Orion VI.