Per the COBRAS help file:
"Restore is supported on Unity 4.0(5), 4.1, 4.2, 5.0, 7.0 and 8.0 with Exchange as the back end. No support is planned for import into any version of Unity with Domino as the back end given limitations imposed by IBM on the DUC interface. Export from system connected to Domino is supported, however."
http://www.ciscounitytools.com/Applications/General/COBRAS/Help/COBRAS.htm
So basically, you can export all the information you *can*.. When you import to Exchange, you will have to match the Alias exported with imported... or it will create a new account for them. (maybe they want this?)
Cheers!