Yes, unless you upgrade to the combox which folks have done. Do a search for vendors (including the tech) who can handle this.
With no combox there is no bluetooth streaming of music available so yes, y-cable is the only option...
2011 Space Grey E90 M3, DCT, Comp. Pkg.
1997 Z3 2.8, Artic Silver, Tanin Red interior, MT
1974 2002tii, Inka, 5 sp manual