Apparently yes they are on a reduced Second officer salary (I don't know how much that is) and either given company accommodation or an allowance to find their own, while they finish their line training. This coming from cadets currently out there.
I'll be honest I don't know much about Al Maha Airlines, but I think they are only for domestic flights within Saudi Arabia (not to or from Qatar). I'm not sure they are even licensed to fly yet so my best guess would be that current QR cadets will do their base/line training on QR aircraft in Doha.
Please remember I'm not at this stage yet so don't know for sure. I am just going by other cadets' experiences and what I can find on the internet.