pbaile-
How do you know the angle should be 90 not 270. Can you give a screenshot or an example explaining this. If you place a fitting by itself look at the orientation. That is what will be 0. Now have revit place the fitting based on other cable tray. Look at its rotation. One things that is a must while doing anything in the API is a revit addin called Revit Lookup. It can be downloaded from here. https://github.com/jeremytammik/RevitLookup
Nate