Yes, there are changes allowing more flexibility in the choice of how to provide your report document to the SubReport item. Please, take a look at this forum post where my colleague elaborates on our considerations for the change: How do you programmatically bind subreports in Q2 2012?
You can also find attached a modified version of the mentioned sample project, created with Q3 2012 SP1, which illustrates how to use bindings
as in the original project and user-defined functions
to set the SubReport item's ReportSource.
I hope this helps.
the Telerik team
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