Extremely common. It's the norm today that companies have firewall/VPN holes allowing support engineers from other companies to have access to their networks,

Extremely common. It's the norm today that companies have firewall/VPN holes allowing support engineers from other companies to have access to their networks, to manage things as simple as the HVAC system, or things as complex as their entire routing infrastructure. Throughout the world, most Huawei routers come with such support contracts.