Yes it’s 100% valid.
Not only you can seat in NET examination but also all government examination where m.tech is required.
I personally know people who are working in DRDO after completing BITS WILP m.tech. Of DRDO accept it’s as valid qualifications then you don’t have to worry.
Unfortunately, in India Work integrated learning is less valued, but all developed countries (including USA, Canada) then give special priority to someone who have work & studied same time on same thing. I believe in India Law, Government, People thinking will change soon, technology enables learning is fastly growing in India, best example is NPTEL online certificate course by top IITs which is widely accepted. Our government will soon realised the need , value associated with this work integrated , technology enables hybrid learning.
Some good thing to tell you all that this year IIT Hyderabad started Work integrated executive M.Tech program. I believe you will not have doubts on IIT offered degree.
BITS is a brand and they have a standard of education and please don’t compare BITS by some xyz University which sells degree through distance education those University are one of the major reason thst India’s overall education system still not able up to mark.