I have a use case where I cannot use the vCenter plug-in to get object properties from an object type and its MoRef ID - there is a bug in vRO 6.02 that prevent to get access to vCPlug-in within Dynamic Types.
There may be other use cases where you may need to do a few operations without adding a vCenter host to your vCO (Different versions to manage, lowering vRO memory consumption).
In any way here is a package containing a workflow allowing to log in vCenter, get an object properties, log out.
Feel free to expand this package to complete other operations.
To capture SOAP messages you can use project Onyx or Fiddler (Windows).
You can download it from flowgrab