  For a normal covering over a closed oriented topological manifold we give a
proof of the L2-signature theorem with twisted coefficients, using Lipschitz
structures and the Lipschitz signature operator introduced by Teleman. We also
prove that the L-theory isomorphism conjecture as well as the C^*_max-version
of the Baum-Connes conjecture imply the L2-signature theorem for a normal
covering over a Poincar space, provided that the group of deck transformations
is torsion-free. We discuss the various possible definitions of L2-signatures
(using the signature operator, using the cap product of differential forms,
using a cap product in cellular L2-cohomology,...) in this situation, and prove
that they all coincide.
