Buying bumblebees

I'm thinking of buying an artificial hive of bumblebees to help pollinate my garden.

Does anyone have experience with these? They seem to be marketed to greenhouse growers, but can they be placed outside in the garden, and will they naturalize?

Bumble Bees? I've never heard of buying them. Tell me more, I'm intrigued.

http://www.koppert.com/Pollination.13772.0.html

I found this paper online. http://www.pollinator.org/Resources/BEEIMPORTATION_AUG2006.pdf

It raises some concerns.

The species I've been considering is B impatiens, which is native to this area, but they seem to be suggesting that problems with parasites might occur if the bees are released into the garden, which is what I have in mind.

CA and some other western states have prohibited imports of B impatiens.