Regarding the Aberdeen and Inverness services being diverted to Glasgow Central, the overall journey time would remain similar for onward travel to destinations south of the mighty Clyde. This is due to the minimum 30 minutes interchange time that has to be allowed when transferring between Queen Street and Central stations.
On Mondays to Fridays peak times, there are some short workings that start from/terminate at Springburn, with services to whats it called? Cumbernauld operating non-stop between Bellgrove and Springburn, then resuming normal calling pattern afterwards.
Ah, Many Thanks