I have a similar issue in Bulgaria. I'm able to setup my Nokia E52 with Nokia Messaging (gmail account). Push there is working fine, but on my N900 although succefully setup, NM push does not work, although the account somehow differ from IMAP only setup. I think I read somewhere that one sign to know you are workig with NM is ability to see pictures and html in mails. I'm able to see pictures and I suppose it is NM but without push.
I still hope I will understand one day how to do the proper setting, till then 30min check interval is working flowlessly.