I've read some interviews with Ukranian tankists. They're using captured tanks. One says he doesn't remember how many he's had to swap because the one he was using stopped working or wouldn't start. The other who also had to switch 'rides' says six.

What I read from that is that partially the Russians left their most problematic gear behind when they bugged out, but also I think that might be a general representation of the state of the equipment the Russians have. So those many thousands of tanks the RF has in storage most probably aren't going to be a major factor.