Part Time B.Tech

Yes, they can join BMS College for doing part-time B.Tech in ECE.

Hello, B.Tech provides the exposure to different spheres in broad manner unlike M.Tech in which one needs to narrow their subjects and have to go via detailed study of the chosen subjects. Therefore, you rather need to strengthen your concepts in graduation on the regular basis for yielding fruitful results in the M.Tech.

Instead of doing part time B.Tech you should go with the part time M.Tech because Bachelor degree is for basic concepts in any course Bachelor degree will give you strong base form beginning to advance. So, as of my point of view, you should go through with full time B.Tech course and part time m tech course.
All the best.

If you would like to do a part time B.Tech degree in Mumbai, maybe you can opt for AMIE or a distance learning programme. https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.shiksha.com/b-tech/colleges/distance-correspondence-b-tech-colleges-mumbai-all&ved=2ahUKEwiPvZLyg6jcAhUMLY8KHUIdArwQFjAFegQIAhAB&usg=AOvVaw2QiYAQNk6AAJ2cTA1jZDCz.

Evening/distance/online/part time engineering courses are not valid any more as per the latest supreme court verdict, hence would recommend you to join regular B.Tech course for better career prospects:
http://www.tribuneindia.com/news/nation/no-technical-education-through-correspondence-says-supreme-court/491819.html

Check the list of all Distance/Correspondence B.Tech Colleges in colleges/institutes in India listed on Shiksha at the link provided below. GET all information related to admissions, fees, courses, placements, reviews & more on Distance/Correspondence B.Tech Colleges in colleges in India to help you decide which college you should be targeting for Distance/Correspondence B.Tech Colleges in admissions in India. https://www.shiksha.com/b-tech/colleges/distance-correspondence-b-tech-colleges-india.

https://www.shiksha.com/search/?uaf[]=location&q=part-time B.tech colleges&s[]=2&qer=colleges|0|0|0|0|145,10|0|0|0|0|0|21|0|0|0|0&sa=^^0^145,10^0^0^0^0^0^21^0^0^0^0^0&tscs=1&sscs=1&ts=52496987&rf=filters&ct[]=64&bc[]=10&ed[]=et_21::dm_34&ed[]=et_21::dm_33&ed[]=et_21::dm_39
Here is your answer.