The old URLs should still work and I believe the ones in the WSDL file are correct. To ensure I'm not crazy, I just double-checked the configuration of an OTM v5.5 CU3 instance and the only servlet mapping (necessary for passing data to the back-end OTM servlets) is still just "/GC3", with nothing setup for "/GC3Services"
At another couple of clients, we implemented integration using the standard WMServlet, based on OTM v5.5 CU3 without issue.
Of course - if you have any updated information, I'd love to hear about it
With OTM, you're always learning.
Thanks,
Chris