I'm not sure i agree on the statement regarding the coaches "all running empty". Sure this may be the case on the new Flixbus 093 and 094 routes and some of the overnight M9s, however for the vast majority of services it's not the case.
I've travelled from Aberdeen to Edinburgh or Glasgow quite a bit over the past few months and each time I've wanted to change to Ember at Dundee to sample their service and found it is fully booked or almost fully booked so ended up opting to avoid it.
With Citylink the M9 often has a fully seated load south of Dundee even with Panorama/Astromegas, while some M92s even leave Aberdeen full. There are some M9s in the late evening that don't carry many passengers but the upcoming timetable changes will address that with a better distribution of services between the M9 and M92 in the evening that should better cater to demand and offer a slightly later service to/from Edinburgh. The biggest issue I have with the new Citylink timetables is that the first direct bus from Aberdeen to Glasgow is now at 8:05 which means you don't get in to Glasgow until after 11am - too late in my opinion if you're wanting to make a day trip and I'd rather avoid the southbound M9s via Dundee in the morning as I know from experience just how busy they get.
Regarding Flixbus, whenever I've seen the 091 or 092 at Aberdeen it has been well loaded, and whenever I've used it the coach has been at least 75% full. The main reason I don't use Flixbus more is because from Aberdeen the first southbound bus is too late while the last northbound bus is too early.
I don't actually think Ember or Flixbus have affected Citylink's passenger numbers all that much; if there was to be any loser then it's probably Scotrail. I do think Scotland is more generally seeing a coaching boom, a big part of which is as alluded to already because of the Under 22 free travel scheme and certainly if the current trend continues then it's clearly disproving the long held view that Scotland doesn't have the demand for multiple operators on the long distance coach network.
Bluebird had to do something as the 10 was at capacity needing duplication or double deckers. I assume that was why they stopped selling Megabus tickets for the 10.
They did for a while operate short workings in the afternoon to Huntly timetabled 5 minutes ahead of the main Inverness service, however in reality due to vehicle shortages at the time the short workings would often end up running empty behind the full length Inverness service which in turn would be fully loaded. The M96 is long overdue and a step in the right direction but the timetable isn't that great due to it being entirely operated by Elgin depot. Ideally it would've been better had just two buses operated from Elgin with the other two operating from Aberdeen and Inverness respectively allowing for earlier and later full length Aberdeen - Inverness runs. The main reason the service is being entirely operated by Elgin was because at the time it was the only depot with sufficient driver numbers.