Here are rules from BA's site:

If you travel on three or more different oneworld alliance airline eligible flights* during the competition period, you will collect the following number of bonus Miles:
No. of different oneworld alliance airlines flown Bonus Miles collected
Three 25,000
Four 50,000
Five or more 100,000

Please note that all bonus Miles will be awarded at the end of the promotional period and at the latest by 31 January 2000.
* An eligible flight is one which is both marketed and operated by a oneworld alliance airline (marketed means that there must be a oneworld alliance airline flight number on your ticket).
** Should first class not be available, you will be ticketed in the next highest class of service.

Nothing about codeshares being ineligible, only that they must be oneworld flight number on a oneworld operated flight.

Copy this web page:

http://www.britishairways.com/execcl....shtml#oneword so you have ammunition if you need it.