While I agree with BC that anyone can call anyone anything, sarkar, raja, mahadev (i dont know, but some women may call their hubby mahadev lol) etc, people also have right to judge those people who are using those words in public.

Kiddo,
I have heard people saying jwai raja, but i have not seen saying nanda maharani. It is ok if these are used with in family members and relatives. But, if you guys have seens, still there are lots of Army, Police and even Nyayadhis and Nijamati hakim family from Shah/Rana/Chhetri (Kaji hari hai) and even Bahun (?) as someone said above (which i am not sure) who want/love to be called RAJA Saheb/Rani Saheb. Especially non-officer level staff working for them use such words for their hakims, well there may be some officers too. Someone may say they dont force those lower rank staff to call them Raja/Rani, well they can just say "Babu/Nani or whatever hami lai Raja/Rani bhannu pardaina hai ". But, they dont.

Ani arko kura, no offence to anyone hai. I have seen a babu saheb ( i mean thakuri) originally from western-region in Nepal has just met with a babu saheb from far-western region in some third country start calling each other Raja ( They are recently introduced and Raja, Raja). And, another bahun/chettri friend who is also part of the group, also a newly introduced person is not called Raja. May be it is reciprocal thing. If you first call another person Raja you will be called Raja in return, i dont know.