  Dijkgraaf-Witten theories are extended three-dimensional topological field
theories of Turaev-Viro type. They can be constructed geometrically from
categories of bundles via linearization. Boundaries and surface defects or
interfaces in quantum field theories are of interest in various applications
and provide structural insight. We perform a geometric study of boundary
conditions and surface defects in Dijkgraaf-Witten theories. A crucial tool is
the linearization of categories of relative bundles. We present the categories
of generalized Wilson lines produced by such a linearization procedure. We
establish that they agree with the Wilson line categories that are predicted by
the general formalism for boundary conditions and surface defects in
three-dimensional topological field theories that has been developed in
arXive:1203.4568.
