Hi, I just found out that it was possible to install a fresh map just bought from tomtom site not only on one Tomtom sd card but also on other ones, provided that they are genuine tomtom sd card.
My experiment early this morning was to install the freshly bought map of Western Europe (v.910) on the tomtom sd card provided by Renault dealer when my bf bought a used scenic there last year. The thing is that the tomtom sd card he was provided with was 3 years old whereas he bought this car in 2012. Thus he decided to go and "cry" to Renault and managed to get another tomtom sd card more recent (this one was 1 year old which was much better!).
Another weird thing that I had noticed at this time was that it was not possible to make a backup of any of these tt sd card, even after trying all available methods. I read on the internet that the reason why it was not possible to do so was that Renault never activate "latest map guarantee" for their cars and just let it expire. I expect the reason they do so is that this way they can exchange any tt sd card with any other car from their car fleet with tt carminat on board.
As a result, it was also possible to install this same downloaded card to the second tt sd card given by Renault without any issue. This way, I finally got a "backup" of my freshly updated tomtom sd card in case I loose/damage it.
I can possibily share my new map with anyone that owns a tt sd card from which the latest map garantee was not activated. Also, I think it shouldn't be hard to get this kind of tt sd card for free from Renault if you bought from them since the age of the card doesn't matter.
Edit: here is the download link of this map (Western Europe 910.4973 for tomtom carminat live):
[Please Register or Login to download file] (this file will be deleted on 04/08/13). Password: navitotal
(activation file: Western_Europe-809.meta.dct)