So, to recap so far...!
The heading flown is always MAG unless flying polar routes. Does it change from Mag to True at a pre-defined point then... e.g above 60 North all headings are flown (and given) as True?
Winds are only mag near the runway (and then only round non-polar airports, I guess). Otherwise they are always given as true. I must confess, I thought most winds were measured from airports (ie. that's where the reporting stations for VOLMET etc were) - does this mean that surface wind is given in Mag degrees, but wind at altitude is given in degrees true?
If you're flying en-route (to repeat an earlier question), what heading is it that appears in the ops room via your ACARS system? Mag, true, or whatever is currently selected via your FMS?
Sorry to keep on like this, but I confess I'm still a touch confused! It sounds as though whilst en-route two aircraft could be given the same heading, and manage to fly true tracks that were several degrees apart.