jBPM has a very open API, so yes, you can connect it. I'm assuming you want to do task based assignments based on AD roles/groups?
Do a bit of LDAP programming and you'll see that there are a number of possiblities.
Related to logging into a jBPM application with AD credentials... you'll set that up the same as you set up any application that uses AD credentials.
I want to connect to ldap from jBPM for users and roles details.
Can you tell me what are the changes need to be done in jBPM?