I can't see any possible way for Bobby to win this fight, this is possibly one of the worst possible matchups for him. Overeem is a highly experienced fighter who arguably has the best standup game in the Heavyweight division, (maybe aside from Pat Barry) on top of that he has an extremely solid ground game. To cap it off he's got the conditioning and strength to match Lashley's pace.
Even if Lashley gets Overeem on the ground via his normal bull rush to blast double strategy, it's likely he'll be unable to hold Alistair down for long, get submitted, gas out, or get swept. It's a complete and total mismatch and I have a feeling we might see another sick knockout like the Overeem/Fujita fight.