Hi. This does not make any sense, if a person is paying for 3G (Data spectrum) and BlackBerry Internet Services (which will use the data) why it should not work?
In my experience these service provider people usually do not talk any sense and talk gibberish. Airtel does provide Blackberry services in 3G. Call up the service providers and ask them if they provide BlackBerry Service in 3G spectrum, if idea has no idea about this then it's useless to use it.