Depending on how your BES admin has the policys set, by default a BlackBerry can be activated on a BES and a BIS at the same time with no problem. I am currently setup this way on my employers BES 4.1.4 and a BIS account for yahoo email.
The service books should look as followed if connected to a BES:
- Desktop [BrowserConfig]
- Desktop [SYNC]
- Desktop [CMIME]
- Desktop [MDS]
- Desktop [BBIM]
- Desktop [ALP]
- Desktop [IPPP]
- Desktop [CICAL]
The service books I have for the BIS account are:
- you@email.com [CICAL]
- you@email.com [CMIME]
Hope this information helps!