If destination data centre is not specified source is assumed. Meaning that they can both be the same.

As for the moveDatastoreFile_Task(), you will find it much the same as cloneVM_Task()

(I use the same variable:VimPortType to call both methods)

See this for help:

http://www.vmware.com/support/developer/vc-sdk/visdk25pubs/ReferenceGuide/index.html