I am not clear about the requirement,If you incoming mail contains any key regarding to the work object(case id,or any other unique property reference of WO),In you listener activity you can just open the WO and update it do a commit.that will fulfill your requirement.
It depends on type of requirement and Architecture you have.
If you want to update a WorkObject on which already a User is working and holds the lock, you need to acquire the lock. It is not a best practice to force acquire the lock while some user is working on a WorkObject which will drag your application into some other problems.
Try out a requestor level DataPage with refresh strategy instead.