I read somewhere that MT eats up a lot of bandwidth quota and there is some plugin that can control this.

Does anyone know about it?

I haven't ever heard anything about bandwidth, but MT does use more server processing resoures than some webhosts give to their cheap hosting plans. I am also not aware of any plugin for this

You will have some issues with your host if your blog is very popular comments-wise. If you have a blog site that gets lots of hits, but doesn't regularly get a heavy commentor load, you (or more to the point, your host) shouldn't have much of a problem with MT.

The things that can influence how much of a load your individual installation of MT places on the server:
* how many sites are you running off of your installation of MT?
* how frequently do you update?
* how busy are your comments? (10 to 20 a day, average; or 50 - 100 a day, average?)
* how many different plugins do you have installed, and do they run every time you rebuild / someone makes a comment?

It's true that, from a hosting provider's perspective, a site with lots of pages that doesn't use any scripts is less of a load, especially in a shared environment, than a single site who is running a mega-modded version of MT (or, for that matter, nearly any script) for a highly active community site. Such sites can (not always do, but can) cause regular slowdowns on the server, especially if the hosting provider has been tending towards the lower end in purchasing their servers, is using extremely outdated hardware, or doesn't plan and communicate clearly with their clients.