We currently have our database objects in TFS2012 and happily use redgate sql source control to check in & getlatest. So far this works great.
I now want to use SSDT in order to create a dacpac that defines the latest schema.
What I'm missing is how to link the SQL Server database project so that a check-in via redgate source control would ripple through to the database project (upon a getlatest) and therefore schema changes would be shown in the dacpac upon a recompile?
As it's 3+ months after I posted the question, and http://blog.stackoverflow.com/2011/07/its-ok-to-ask-and-answer-your-own-questions/ I guess I should state what the outcome was...
We had a number of unresolved (at the time at least) issues automating SQL Compare, which was the reason for looking into SSDT in the first place. The more we looked at SSDT the more we became impressed with it (still has some issues, but doesn't everything?) to the extent that we have now dropped our use of redgate, therefore the need for SSDT to play nicely with redgate is no longer required.
This is not to say we're not a fan of Redgates products or that the answer is to drop redgates products - just that they didn't meet our requirements when our requirements changed (we started to automate everything).
I'll still be sending Redgate a Christmas card, honest :)