never thinked about it, but i know that Chugaev Reaction (Tschugaeff Olefin Synthesis) generate only cis olefinic products, so i suppose that you should obtain only cis olefins also with the cope elimination.
In addition i found this:
Mechanistic study: R. D. Bach, M. L. Braden, J. Org. Chem. 56, 7194 (1991)