Bottle yeast May/May not be the same as the yeast that the beer was fermented with. Culturing yeast and using bottled yeast as a starter are different. I just started culturing yeast and for $50 I can now save any yeast for up to a year with no ill effects.
What I have done in the past for using bottled yeast as a starter:
Make a small starter (1qt) of 1.040 and chill as normal. Take two bottles of the beer. Spray them with StarSan. Open them. Flame the opening (Hint: Get yourself one of those wind resistant Lighters, they work great for this). Pour the beer out into two glasses (for medicinal purposes) leaving about 1" of beer/yeast. Swirl the bottles then add to the starter as normal. This will give you enough yeast to make a larger starter of 2q.
Don't forget to drink the two glasses of Beer... ;D
If you are interested in culturing yeast, here is some good Info. Darin helped me allot with my project, however I have not seen him on in a long time.
http://www.beersmith.com/forum/index.php?topic=2291.0
http://www.beersmith.com/forum/index.php?topic=657.0
http://www.beersmith.com/forum/index.php?topic=2365.0
Cheers
Preston