Need opinions on servo motor control for heavy applications
For industrial grade applications, a more typical arrangement than the conventional servomotor, is a suitably geared down 3 phase motor, with either end-stop detection, or some form of position encoding, controlled by a HVAC (or main line voltage) control circuit, either switched or PID based. 

For instance, in railway locomotives, while the pantograph seems an ideal candidate for a big servomotor, that is rarely if ever the mechanism used for extension and retraction. Note also that pantographs are not always two-position, some designs have fairly sophisticated sensing mechanisms and fine position and pressure control.

Another typical actuation mechanism for the kind of motion you are describing is the use of pneumatics or hydraulics - you can see this in the lift arms of fire trucks, for instance, or as the actuators for garbage trucks. This prevalence of liquid / gas drives instead of electric motors is for at least a couple of reasons: Safety (electrical failures and fail-safe modes) and flexibility of power routing. It is easy to have a compressor far removed from the moving parts, and just use piping down to the actuator. 

Again, there are a number of sensors involved, to ensure precise positioning with such actuators. This is either in position steps, or fully analog sensing. There are also usually independent channel end-stop sensors to account for catastrophic failures by engaging some sort of fail-safe. The positioning, either way, is via external feedback channels rather than the integrated model used in hobby servomotors.