There are very few yeast strains NOT available to us as homebrewers that would be exclusive to microbreweries. They may have, through adaption/mutation come up with a house strain, but I doubt, since their are giving it away that it is a proprietary strain unless of course it's rogue, and you are getting pacman slurry, but even that can be bought or harvested.
Many of the micro breweries brewing ales, use the chico strain, some that I know in Michigan use 1338 Euro Ale, but an equal number of micros probably use fermentis or Danstar dry yeasts, like we do, just in huge quantities.
BUT the benefit of the free yeast (besides being free) is that they will have pitched huge amount of yeast meaning a huge cell count. And just as when we pitch onto a yeastcake from our previous batches the yeast is going to be extremely active, quick starting and tenacious.
So enjoy the gift, but you need to find out which strain it is, and whether it is an ale, or lager strain, of something like Pacman or Cry havoc that can be used either way.