I have a SPSiteDataQuery that I am giving a set of list ID's. The set of lists are both Generic Lists & also Libraries. The issue is my Libraries are not being returned. Is it possible to search both Lists & Libraries with SPSiteDataQuery?
No, You can only query a specific type of list. SPSiteDataQuery use the template id to return the rows. so for document library data, you need to add another query for that.