Each ITSM end point has its own adapter. So, you would configure and enable an adapter for each ITSM end point. Then you would write workflows or re-use OOTB OA modules to interact and these ITSMs.
Is there any scenarios available for these adapters...? and what about using web-services..?
Not sure I understand this question: "Is there any scenarios available for these adapters...? "
BAO supports using web services , but one needs to see if target ITSM supports web services. Remedy ITSM has web services, but I personally prefer BAO's Remedy adapter because it is more flexible and can with any form in Remedy ITSM. SNOW exposes web services API as well and BAO's SNOW adapter uses web services.
There are two ways to integrate BAO and ITSM tools,
2. Web service
Here, we can consume BAO's web service in ITSM for monitoring the records at the time of creation/updation, then we can use the validations using XSLT or switch cases for updating any particular ITSM environment using adapter(if there are 2 different ITSM environment).
If you need a more sophisticated approach to integrating multiple service desks and synchronizing updates between them, have a look at this AO based offering
TrueSight Orchestration - BMC Software - E- Bonding solution.