For those who did not see the downtown's "original milepost zero" location at 102 Avenue at 10 Street - this is a picture facing the southwest corner in September 2011 :

Facing northwest corner - overlooking north end of 10 street at Alaska Highway :

Mile 0 Alaska Highway at 10 Street facing east near historical roundabout :

Roundabout intersection at historical and world famous signs with plaque monument :

I also wondered about how which of these two locations was the more significant 'true' mile zero.....
I assumed the downtown sign was in place for the readjustment of the true distance starting point, as the roundabout area was the more closer spot of the original location as the historical signs and plaque were in place there as for whatever reason the roadway around there might have been revised (as was my guessing)....Now that explorenorth has clarified the roundabout intersection is the original starting point of the Alaska Highway all along.