[pfreivald]

The polycarb acts as a spring to space out the wheels so they fit around the pole. It's held in place with a bracket on the HOSTBOT which is punched out by a plunger on the MINIBOT when it hits the pole (this plunger also turns on the wheels, and another one turns them back off when it hits the plate).

So the MINIBOT is 'squeezed open' and held in place by a post on the deployment mechanism, then snaps in place and turns itself on using the HOSTBOT-imparted lateral kinetic energy to pop the plunger. It then drives off of the post.

Edit: Attached is a closeup shot (a bit blurry) where you can see the wheels and plunger, as well as an Inventor drawing of our deployment mechanism. (The carriage is deliberately a bit massive. This is not a subtle device!)