Does IIEST Shibpur provide a good placement for M.Tech?

No, it is more or less the same as a bachelor's. Not just at IIEST Shibpur, the scenario of placements for Masters is more or less the same at every institute in India.

If you pursuing Masters then you should keep your aim straight to get a Company related to your branch or pursuing higher studies (Ph.D.) for the teaching line. B.Tech level hiring is more or less the same in M.Tech at the institute. There are some departments in M.Tech which have a moderate placement. The other departments do not offer good placement opportunities. But at IIEST Shibpur you will get the best learning opportunities. 

At last, it is up to you only which field you are choosing. If you want a job then go for it with for B.Tech degree, If you want a purely technical job then go for a master's and if you want an academic line then go for further higher studies i.e. Ph.D. from abroad.