i do not personally believe that TRAI would want to set pricing for the companies operating in the market. in a democracy, they cannot force anyone to price their services below a certain level. of course they do have upper limits for some aspects of the services. but generally speaking, they have no logical reasonings to enforce a pricing scheme when there is no monopoly in the market.
how would you feel if the indian government enforces a ruling that for the job you are doing, you cannot get a salary above a certain limit? it does not work out like that.
TRAI is already setting the prices of mobile phone services. For example, termination fees of phone calls made from one cellphone operator to another is fixed by TRAI and it is 20-30 Paisa per minute. SMS sent for one operator to another are carried without payment of any termination fee. So, we see SMS cost as low as 1 paisa per SMS in some plans.
If they can fix cellphone tariffs indirectly, then why not broadband tariffs by controlling the cost of wholesale bandwidth?