I'm not sure if it was fixed in the nights. ???
(https://www.mediafire.com/convkey/5cce/b0a9lnlfa7au1ad6g.jpg)
I think the bug more is that you are allowed to build a single height bridge over a power line than the graphics messing up when you do so. Power lines I believe are meant to have a clearance of 2 (they occupy the tile directly above the ground as well) as such the power bridge shown should not be constructible. You should need to first elevate the power line 1 tile above the line you are trying to cross and then bridge across there.