I'd apparently successfully repressed my memory of that abomination against good sense.Victor is in production on Quentin.
Quentin and St. Ives production sites make it a thing the Dracs are very unlikely to want to not come crashing to the ground if it tries to stand on one of their buildings and not something the FWL would be particularly keen on supporting, though unlike the Dracs they're probably not particularly eager to sacrifice civilian urban buildings to inconvenience their enemies. There's also not particularly much reason to reinforce to that degree on the Lyran border where neither side has been fielding stuff over 65 tons that can actually get onto a roof.
Building a non-mechproof building near a border is like building a non-earthquake-safe building near a faultline. Something that people do quite frequently if not forced to build to higher standards by building codes. I can't imagine either a nation as internally divided as the FWL nor as uncaring of its subject's wellfare as the Combine enforcing such codes generally. Maybe some wealthy and paranoid border worlds in the FWL have such standards for mechs not being fielded by their own militia or common in their nations national forces, but if the Combine is enforcing mech safety building codes they're probably something like "must support a Panther but collapse if someone tries to stand a Phoenix Hawk on it unless it's an important enough building to merit maximum reinforcement against deliberate bombardment" because the DCMS seems to have a policy or stripping jumpjets from everything but Panthers and Quickdraws in this era and Quickdraws are not designed to be rooftop snipers.
I can't find a surviving site off Terra which means the Comguards have them, but anyone else should get significant numbers only if it serves Blake's Vision. Starcorps' Fletcher site was destroyed in the 1SW and Hollis lost their factories in the second. Something like a sudden deal to supply the Capellans or some of their long term contracted mercs going through after Maximillian Liao was replaced by a doppelganger if we go with that theory for his personality change might have effected new construction in the FWL near the border after a few years, but wouldn't probably be enough to lead to mass refits.You are right that it's a 90 tonner. However, it stopped production on Son Hoa, in the Lyran Commonwealth.