Do Bluray releases contain more scenes than their DVD counterparts?
Yes and no, much like any other blue-ray content (e.g., movies). 

When releasing the blue-ray version, the publishers will always want as many people as possible to buy it. To do it (especially if the Blue-ray release follows a TV release and a DVD release which means a lot of potential customers have already bought something), they need to somehow raise your interest to the blue ray. Since a Blue-ray disc provides much more space than, say, a DVD disk, that gives them a chance to interest you:


Higher quality video
Higher quality audio (e.g. lossless audio formats)
More audio tracks (original audio, dubbed audio, maybe an audio commentary from the authors, etc. etc.)
Additional bonus content (interviews, films about "how this was made", soundtrack, and so on)
Bonus scenes/director's cut.
Other merchandise (posters/books/artbooks/anything-else-you-can-imagine-just-pay-for-it).


For example, here is the Fate/Zero Blue-ray box, which costs a hell lot, and includes, among other stuff, 


  
  Extras: New bonus animation (written by Kinoko Nasu), Trailers, TV Spots, Textless Opening and Ending
  Episodes: Episodes 1-13 with unaired new footage
  


However, I wouldn't say that "most of", or at least "a lot of" Blue-ray releases contain bonus scenes, but unfortunately I can't prove myself with any facts, because apparently there's no such statistics in the Internet.