ISRO accepts an Engineer who have graduated with BTech/MTech with at least 65% or 6.0 CGPA score.

The degree offering institute must be recognized by the UGC/Government of India. So yeah! If you go for the course of Engineering in IIEST then you are eligible for the ISRO jobs. You will get the job is entirely dependent on your intellectual capability and skill. ISRO don't provides any special preferences to the student of IIT's/NIT's/IIEST etc, but most of the candidates from this institute gets the job in ISRO because, they are good in there subject. So if you can build up your skill, then without any doubt, you can go for the job profiles offered by ISRO.

For more information regarding IIEST consider the link below:

https://www.careers360.com/university/indian-institute-of-engineering-science-and-technology-shibpur

I hope this helps. Wish you a great day!