China has claimed to have made progress on the electronics and power systems for aircraft carrier magnetic launchers.
A Chinese land-based version of an aircraft carrier magnetic launcher already exists at Huangdicun Airbase in China.
China would likely not look at making a lot of modifications to this system. They would likely just build the exact same system on a Tibetan plateau.
Aircraft Carrier magnetic launchers
DigitalGlobe imagery captured on 1 November 2017 showing a J-15 at the catapult test facility at Huangdicun Airbase in China.
If China is looking to adapt aircraft carrier technology for mountaintop rocket boosting, then they must be looking at smaller rockets.
If they were using the 300 foot long launchers, then doubling the speed would mean four times less mass. A 6,000 pound rocket could be accelerated to 600 miles per hour. A 1500 pound rocket could be accelerated to about 2400 miles per hour.
It would be simpler to keep the accelerated missile just below the speed of sound for the magnetic acceleration. The missile might get about 30-50% savings in fuel from the magnetic accleration. Range could doubled because of the advantage of higher altitude.
It the system had ten times less power than an aircraft carrier launcher then it would be 600-pound missile accelerated to 600 miles per hour.
NASA has looked at adapting aircraft magnetic launcher technology to make a 2-mile long launcher to get larger orbital rockets up to mach 10. China will not scale up to such a large launcher for their mountaintop system.
The mountaintop launcher would not look like a traditional truck-based rocket launcher. A truck based system would not allow the magnetic system to be large enough to accelerate a damaging missile.
There was a university student analysis by Saranapob Thavapatikom for using a 32-megajoule railgun to assist with a rocket launch. If a railgun launcher had 33% conversion efficiency, then 27 MJ of electrical energy could accelerate a 3.9 kg projectile carrying a 1 kg payload to a speed of 2.1 km/s. This would be able to reach 120-kilometer altitude.
A closer to truck-sized railgun would be able to accelerate small artillery sized projectiles.