X1 isn't based directly on the 1 series. Its based on the E91 (previous 3 series wagon). Look at these wheelbase and track measurements on Edmunds...X1 is identical to E91:
X1:
http://www.edmunds.com/bmw/x1/2013/f...426442&sub=suv
E91:
http://www.edmunds.com/bmw/3-series/...8752&sub=wagon
1 Series:
http://www.edmunds.com/bmw/1-series/...1665&sub=coupe