DiGi will be just another small time isp in Malaysia which will not be able to take on the megabits challenge.
It would cost them a lot for international leased circuits, setting up their own fiber infrastructure backbone and data centres.It's going to be a hefty investment for them.When their subscriber grows, they'll face the same big problem of sustaining the service quality and ensuring that bandwidth is enough for everyone.

Look at Maxis, they already imposed line barring even after a few gigabytes of data traffic. How do you think DiGi a much smaller company can pull off a stunt better than them?