Yes , TI does offer that facility and that was precisely the reason I opted for it. I am reproducing from their FAQ's below
Q1. Can a Tata
Indicom Broadband subscriber avail Dial up services on the same account?
Ans.: Yes. Tata Indicom Broadband brings you the unique flexibility that allows you Dial-up access on the same broadband account.
Since I use it mainly for email purposes and to keep in touch with my office it makes more economic sense to use a dial up from remote locations. Of course I do have a web enabled phone but the dial up beats the hell out of all other options costwise since you have to dial a local number to connect.
Yes you can connect using a BSNL/MTNL/Tata or any other line having that facility.
Oooohhh....and you fell for it?
Thats why TATA is still in business
Dude, do you know the meaning of this roaming account? Suppose you're in bombay and you dial a local number to connect to TATA. Now you decide to move to Chandigarh. And from there you wanna use your "roaming" account. So you call up the SAME, Bombay number to connect to them. You know what the cost will be? It will be equal to the cost of calling up from Chandigarh to Mumbai which is pretty hefty plus whatever per hour charge TATA levies on you! Hahaha....