For those of us still needing to use Revit 2009 and 2010, Cooper B-line has made some nice cable tray families for us to use. I was stuck for a long time with using ducts or custom made families that didn't really work properly. These seem to be working fairly well so far.
The one thing that I have noticed is that they seem to still show an interference when you put a corner on them. That is, when you do an interference check, there is conflicts with equipment that doesn't intersect your cable tray. I t is like the cable tray extends past the corner and into what it is interfering with even though you cannot see it in any view.
As you can see, Revit is telling me that the duct (in red) is hitting the cable tray (selected) when they are obviously not. You can tell from the interferences on the list that this is happening in a number of different places.
As long as you and your mechanical engineer are fine with checking these conflicts manually, these cable trays come together quite fine. They are pretty easy to use and configure. You can download them here:http://www.cooperbline.com/contact/BIM.htm