I am assuming the english site is www.thesite.com, then the french site is www.thesite.com/french, and would be linked from the English site, perhaps page by page. Wouldn't it therefore be the case that my page rank would get some benefit from the English site?
When adding a brand new page in English, even if I have no links from external sites to that page, the rank will not stay at zero for long (I think!).
Does google care whether the inbound links are French for the French site? I would have thought so because of the relevance to the linked page.