I downloaded beta 3(using as plugin in eclipse 3.5.1) and I still can't wrap snippet tags around existing code. You should be able to apply a snippet to existing code without deleting it as cfeclipse does this just fine.
Currently, the snippet gets inserted in the selected place in editor. We have this ER in the pipeline whereby the selected block of code gets wrapped up with start and end block of the snippet.
Adobe ColdFusion Team
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