If you are basically asking if you can do something like a db backup of ms sql and restore it into another version in Oracle to a system where you do not have a system level access or if there are tools in Clarity or third party tools for that the answer is no as Dave already answered. Even with an on premise and using the same database the version hop may give hickups.
This has been asked for more than once. Search the message boards.
What you can do is XOG out what you can as Dave posted. You can get further than that with SQL queries with or without portlets. That is for reading the data out.
The writing of more than standard XOG xml data is possible with GEL scripts or tools that use GEL. However, with on demand the tools has to be such that requires no install on the server and works on the client only.
There are commerical third party tools and CA Services Data Migration tool, but I am afraid they require installation on the server but not sure of that. Secondly the price may not be justified for a single migration.
Martti K.