The above is true but in fairness to First, they have revamped the north western Glasgow services with some of the longer services diverted via the A814 - the old 16/44 to Knightswood are now the X4, the 9 to Drumchapel is the 1C, the far end of the 62 (or 66?) is now the 1D... that area has had more of a transformation than most of the rest of Glasgow. The X85/X87 have replaced many of the slow journeys on the Bishopsbriggs corridor towards Kilsyth.
I guess the question of any "express" service is whether it replaces many/all of the journeys on conventional services into Glasgow and whether you use many additional resources - for example, if there's to be an express from East Kilbride into Glasgow then is there significant enough demand for (e.g.) East Kilbride - Rutherglen services for some kind of "legacy" service to continue? Or would it end up like Knightswood, where the X4 runs "fast" into Glasgow but there's no service from Knightswood to the Byres Road/ University area (that the 16/44/44A used to provide).
The extended M74 seems like it'd have been an opportunity to revamp services but... no... there are lots of stopping services to Lanarkshire each hour but only a tiny amount via the M80 (the X1 and X11).
The X1 and X11 don't operate via the M80 and never have.