I found an Italian website that ranks number 10 for a kewyord on google. It has been created on 19 Feb 2009. I searched its backlinks by yahoo. Yahoo shows to me 29 backlinks: 28 are from English websites and one is from an Italian website with no pr. That means the language where is placed the backlink does not care. It seems to me as a no natural links (if you own an Italian website your backlinks should be in Italian pages), but google accept it. Just to let you know.
What it means is that those backlinks can be spidered and indexed - no matter the language of the page where they appear. But the observation doesn't say much about what effect those links actually have. Google and Yahoo both will list backlinks even if they are contributing nothing to the ranking.
Are you saying that Yahoo does not show at least the 90% of the backlinks of one website?
Not at all. I'm saying that just because a link is showing that doesn't mean it is helping the site on Google (or on Yahoo). Both search engines will show links that are being devalued by their ranking algorithms.
I also agree with Ankit - a link from a site in another language but still on-theme is helpful.
still quantity is able to beat quality in a short to medium term (i.e. until you get a -50 penalty for crap backlinks from Google). I mean: loads of non-topic, different language links will eventually get your site to #1 as long as the domain is trusted enough. Only problem is you need to risk a domain that has trust already ;)