Id for the Quest is MS11b but I have tried startquest MS11b and it has not worked. Even tried doing the command Help MS11b 0 and it gave me a lot of options for the quest id but still nothing has worked.
The questid might also just be "MS11", and the console lists a long, hex code for it too. Perhaps the hex code has to be used rather than the MS11 quest id?
Either way, I've been unable to figure out a console command to start it. "StartQuest" didn't seem to do anything for me as well, but there are a bunch of other console commands that show up if you type "help quest" related to quests, so there might still be a command that'll work for getting it started.
One of the console commands, for example, showed me all of the objects, and my current status on them, for the questline. Considering I didn't have the quest, it showed "Dormant" for every objective. I could not figure out how to set any, like the first, to active.
But if anyone could figure out a console command that seems to do something...
Edit - Something else interesting is if you do "help ms11 1" you see some stuff related to the quest, the global variables listed are what's interesting - it seems to record how many times you have been to Windhelm, and something about "Followupday" which for me is stuck at 0.00