I am not advocate and a banker.
Proper course is taking an advocate into confidence. When your friend is in possession, they can not make forcible eviction and approach through court of law by paying court fee at Current market rate against a party who is not concerned with the loan. There is limitation period for every action. The Bank is aware that their borrower has alienated the land long back, but not taken corrective step and abetted his fraud indirectly. The banker is fighting from a very weak position and can not risk of spending good amount on a losing cause, when neither documents nor facts support his stand.
Please contact advocate as stated as these kind of guidance is not proper way without reading the documents and studying deep into the issue.
Before all that, ask your friend to file RTI Application to the Bank seeking certified copies of all documents available in their files basing on which the citizen is being harassed. Hope this will silence mostly, if banker is at fault.