This may have to do with the tiger being changed but upon starting M08 of the Soviet Campaign, the Tiger that is supposed to appear, simply stays in its building all day. Waiting. And the mission never progresses. The Soviet tanks will call out "Tiger!" But nothing will happen. Here are some screenshots of this event, but I implore you to try it yourself. As I have tried numerous times now, and for no reason what-so-ever the Tiger just, doesn't want to come out and play.
Nameless scripted tank and SU-76m after the Tiger script was supposed to start
Frontovik squads moved near the nameless T34 in a desperate attempt to trigger the event. Nothing still happening.
Screenshot of all the tanks after they have called out a "Tiger" and no Tiger has appeared.