Does "submitted to Thomson Reuters" mean that a publication will actually be indexed? I have seen a few conferences that state on the call for submissions that the conference will be "submitted for indexing in Thomson Reuters Conference Proceedings Citation Index (ISI Web of Science)."  

Does submission mean they will 'apply' and could be rejected, or are all submissions accepted?
It does sound like rather tentative wording.

Thomson Reuters cannot, would not, and should not accept all and any submissions of anything for indexing - it would swamp the system with spam.

So to me, it sounds like the conference has applied to be indexed, but it is certainly not absolutely guaranteed that they will be included in the Thomson Reuters Conference Proceedings Citation Index.