They can. My second Jool mission was a Cassini-like probe powered only with one ion engine, i put 2k ec in it an fired at the dark side to enlarge my apoapsis. At the third time, i just kept firing the engine and set course for jool.
This is probably one of the best and most challenging Challenges. When I finally somewhat complete my Career Playthrough and move on to 1.1, I will come back to this.
I actually drove across minmus equator with an electric rover, it sucks and you need to have damn good reaction to put the reaction wheels on if you don't have such a genius idea as the guy with the triangular wheels. It works.
Pleeeeeease, Update to 1.1. I love your textures, they are waay better than the stock ones. Only one thing annoys me: the docking port hitbox. When docked, it doesn't really look like it's together, there is some space in between.