I went to another dealer last 3 weeks to check the E90 & was told I can get the pre-owned year 2008 units. I forgot to ask about the warranty but I believe it will still be 3 years.
For the E46, being the previous model, getting a 6 months warranty from the authorised dealer is not a bad deal. If you buy from 2nd hand dealer, you'll probably get 1 month warranty and from private owner, maybe 1 week. So you gauge which is best. Now you have several authorised dealers you can choose from - 3 in kl and many others in other state. I for one am looking for a E46 for my wife come 2009, may consider at any available BMW dealer pre-approved/pre owned unit. But hard to come because it will depend on any owner doing trade-in.