Drew,
You might find some of the information in these articles useful:-
http://www.frenchentree.com/france-satellite-tv-internet-pcs-telecoms/DisplayArticle.asp?ID=7430
http://www.frenchentree.com/france-satellite-tv-internet-pcs-telecoms/DisplayArticle.asp?ID=7495
http://www.frenchentree.com/france-satellite-tv-internet-pcs-telecoms/DisplayArticle.asp?ID=7531
I'm not sure exactly when these articles were written but I think they're 2007.
It seems that the basic setup, and the costs, of telecomms in France is very much like it is in the UK. As far as ADSL is concerned, France is a much bigger country, of course, and telephone subscribers out in rural areas are therefore likely to be distanced considerably from the nearest exchange. However, this shouldn't worry you personally, as my understanding is that you'll be moving to somewhere like Lille. Thus, if you're living 'en ville', you're much more likely to be near an exchange and should therefore get a reasonable ADSL speed. I'd still advise that you find out the location of the local exchange, in relation to the house or flat where you'll be living, in order to calculate the distance. I personally would want to keep that distance to 4km or less.
The author of the above article on ADSL reckons that the local mairie has a big say in where and when ADSL is provided, if it isn't already on tap. so if necessary the appropriate dept of the mairie should be approached. Perhaps you or your partner could contact that dept by e-mail right now, to check? This seems to fit with the way that local infrastructure and planning approval are traditionally dealt with in France.
If I find any other useful articles, I'll post them here. I've printed out some of them for myself, actually, as I too am interested in how telecomms, as seen by the consumer, works in France.