Custom PowerShell Provider and Copy-Item between logical "file system" Providers

Hi,

I am trying to write PowerShell provider for Skydrive, Dropbox and other file like files stores.  Unfortunately, I am having trouble getting Copy-item to work from the local file system up to my provider. The following error is returned: 
     "Source and destination did not resolve to the same provider."
Logically I am copying files between providers and can fully support the copy operation.  How do I avoid the error and handle the copy?  It appears that my PSProvider's override of CopyItem() does not get invoked before the error is thrown so it is not clear how I can intercept the copy operation.

Thanks,
Mark