E46 rims WILL fit the E90
One of my dad's friends successfully mounted 2000 E46 325ci 16in OEM rims into his new 06 E90 325i (205/55/16).
I went to look and test drive myself- the wheels are sunk into the wheel well a little bit- so a looks a little wierd, but otherwise, the tire clears everything- the shocks, the wells, fenders- I tried full lock both directions and no problems.
The only thing I could see was clearance between the caliper and the rim was tight- so different rim shapes *might* have clearance issues...otherwise, don't waste your money!!