I do not know what drives you have but as said earlier it is normal for servo drives to have a means of enabling/disabling a brake.
If your servo drives do not have that option then the best option would be to have the brake connected to one of the enable outputs in Mach. That would mean when when you take Mach out of reset the drive would get enabled and also the brake would be released.
If you require the brake to be only released at specific times then you would have to do something different but without knowing exactly what you are trying to achieve it is impossible to say what would be best.
Hood