Planet13 - 8:54 pm on Aug 3, 2013 (gmt 0)
If it makes sense for USERS then google probably won't have a problem with it.
But make sure that you redirect the appropriate pages to the MOST appropriate page on site B.
If you DON'T have an appropriate page on site B, then you would probably be best to either create that page on site B, or just 404 the old page.
One think you DON'T want to do is redirect a bunch of pages from site A to the home page on site B.