If you read some older posts about this topic you'll see some people will say "no, never" and others (like myself) would argue that many employers do call your previous employer regardless of where they are in the world (as long as there isn't a language barrier). Time differences are not a big issue. If I have to call someone at 8:30 p.m. my time to get them at 8:30 a.m. their time, I'll do it -- this is common in Human Resources.
I can only speak for myself and a few other HR people I know, but I definitely call your references regardless of location. I want to know first hand how you worked, any issues, challenges, successes etc.
Written references are not as important any more - not to say if you have one you shouldn't present it (at the appropriate time) but good reference checking is done via phone.