Probably not so much western parts. Also regardless of China’s national policy individual Chinese companies regularly get sanctioned and are effectively forced to chose between doing business in the West and Russia. Which obviously isn’t a very hard choice for most…
AFAIK most stuff is smuggled through countries in Central Asia and the Caucasus (with no negative consequences for those countries; the opposite really..)
I'm not versed in illegal imports, but I suppose they're both more costly and more sparse than the regular channels. With russian airlines probably not being too flush with cash atm, something's gonna give, and that would be maintenance beyond absolutely necessary repairs.
