nik_in,
First, there seems to be nothing in the information that you have sought, which could have possibly convinced the
PIO that a thrid party can object.
Secondly, how did the Indian Hotel & Restaurant Association come into the picture ? If anything, in this case, the Third Party could have been the Hotel Owner. It looks as if the
PIO has informed the association about your application and brought up an excuse to deny you the information.
Please read the BMC Act sections 394 and 412A, which cover licensing and controlling of trade dealing in food. I cannot find a online copy of the Act. There must be similar sections about Hotels. In any case, the Hotel you referred to has a restaurant. As per my experience, restaurants and eating houses have to display the license obtained in public.
(For example, in AP, every Shop and Establishment needs a license and that has to be displayed duly framed, in a prominent place EVERY YEAR after renewal).
I am sure the situation should be similar in Maharashtra.
If the license issued is "public" then the application made for the license should also be public. It is a "public" eating house and a hotel...with "rights of admission" and therefore there can be no denial for the information you have asked.
If you are still within the time limit, please go in for First Appeal.