Regarding buses Glasgow - Airdrie, I can also remember the 213 that ran via Royal Infirmary, Edinburgh Road, Baillieston, Bargeddie Station, then direct along the A89 via Coatbridge to Airdrie bus station and onwards to Petersburn.
This was before the Overground concept in 1999. The 213 was curtailed to only run as far as Bargeddie Station, with it most likely to have been operated by Parkhead Garage. When the garage at Possilpark closed in the summer of 2000, I am unsure if it was the 213 or the 203 that ran to Cairns via Cambuslang that got incorporated with the 184 that used to run to Kilsyth via Twechar. Whichever one it was, it was split not long afterwards due to delays across both sides of the Clyde.
Also, the former 184 Glasgow - Kilsyth via Twechar I believe was the only former Possilpark Garage Kirkintilloch route that did not transfer to the garage at Cumbernauld (Carbrain, just past the railway station and subsequently transferred to Stagecoach Ayr division - not Fife Region), whereas the 88 Glasgow - Harestanes, the peak Waterside via M80, and the 175 Campsie Glen did.