A rather amusing Indian article on Yaks claiming their hooves behave as suction cups. Discounting the Indian nonsense, we recently had the case of a PLA soldier in Ladakh assisting Yak herders.
Are Yaks still in traditional use in China in those mountains? Unlikely...
China has excellent infrastructure for transport of materials as well as an advanced dairy industry. Prepackaged cheese, butter condensed milk, are easily transported. Due to the small population of Yaks their wool also is likely available in very small quantities to substitute Merino sheep wool or synthetic fiber. As pack animals over uneven terrain, snow mobiles, and ATVs could do everything a Yak does and more.
Found in Himachal Pradesh, Sikkim, Arunachal Pradesh and Ladakh, the yak is the most important species for highlanders in these areas. In Ladakh, it faces one of the harshest environments. It feeds on grass with leaf blades barely an inch long at high altitudes in the summer, descending to lower ranges in the winter. An excellent pack animal for snow-bound areas - its cup-shaped hooves create a vacuum, allowing it to walk easily on ice - the yak can cover 25-30 km per day, carrying loads up to 125-150 kg.