Surrender of tenancy rights

First of all, Sec50C will be applicable in case of immovable property especially Land or Building transfered for Inadequate consideration not in case of  "NIL Consideration". In your case it is an "Intangible asset"  and indeed for "NIL consideration" so Sec50C will not apply.Because if it is for "NIL Consideration" then it will be taxable in the hands of Receipient provided receipient is not a Relative u/s56.So in your case if the Fair market value of such tenancy right is above rs50000 then it will be taxable in the hands or Landlord as "Income from other sources"

I think Bombay Rent Control Act shall apply here. 

Have you been paying rent to the landlord for all these years? Do you have all the rent receipts? If yes, then the tenant may demand a compensation from the landlord for surrendering his tenancy rights. The court cannot pass a decree of eviction against the tenant. You may negotiate with the landlord to pay something for surrending the tenancy rights and handing over possession of the flat.    

Inadequate considerations means any amount which is less than s.50c value, unless disputed or referred for valuation. So this will include NIL conideration also

But the Q is, does 50C applies in this case?

S.269A definitions

Immovable property” means, - (i) Any land or any building or part of a building, and includes, where any land or any building or part of a building is transferred together with any machinery, plant, furniture, fittings or other things, such machinery, plant, furniture, fittings or other things also.

Explanation : For the purposes of this sub-clause, land, building, part of a building, machinery, plant, furniture, fittings and other things include any rights therein

But There is this judgment Kishori Sharad Gaitonide V ITO (ITAT MUM) wherein it was held that S. 50C does not apply to “rights” in land & building like tenancy rights

It is trite law that a legal fiction cannot extend beyond the purpose for which it is enacted. As long as there is no ambiguity in the statutory language, resort to any interpretative process to unfold the legislative intent is impermissible. The statute has to be interpreted on the basis of the language used. No words can be added and only the language used can be considered so to ascertain the proper meaning and intent of the legislation S. 50C does not apply to all capital assets but only to “land or building”. A tenancy right is not “land or building” (It is “rights” in building).

S. 50 c uses word capital asset being land and building

Govt. wouldn't be much happy with this judgement and this is at ITAT level , so lets see

But if we follow this judgement then no 50C in your case, What is received in relinquishing the tenancy right would be your income chargeable to tax, since nothing is received hence no tax