To answer your original question studios will use different proprietary software but no one knows every single rendering engine on the market so don’t worry about the software, worry about learning how to actually light things and then you can start thinking about vray, maxwell, renderman and so on. If you’d work at a studio in the future they will train you in their specific software, it’s about learning the principle and techniques in one app.
If you have Maya then learn how to render in maya software and mental ray, maya software is fast and simple if you look in you render settings you have only one tab while for mental ray there’s four so more features and more complicated. Mental ray has additional materials and allows for indirect illumination which allows for better results, but also higher rendering times so it’s good to understand the fundamentals before starting to turn things on.
You need two things to get anywhere in lighting the first one is an understanding of how lights and materials in the real world works so make observations. There’s a good sticky thread with a tutorial on this http://forums.cgsociety.org/showthread.php?f=21&t=209619.
The second thing is an understanding of CG lighting, Jeremy Birn probably made the best tutorial on this topic you’ll find it in the shop http://store.cgsociety.org/product/000447/ it will take you through a lot of topics and if you follow that it will give you a good understanding of maya software and mental ray. He also wrote a great book called “Digital lighting and rendering” which you definitely want to read if this is a field you want to focus on.
The lighting challenges on this forum are also a great resource, you can download old scenes for practice on your own or participate and get some feedback from other people. So don’t worry about the software, but focus on the techniques which is what really matters in the end of the day 