I don't know anything about telecoms, but I work in a different area of software development in China and can confirm it is not uncommon for developers here to bring their whole previous employer's repo with them when they switch jobs. One of my most cringeworthy moments was when I saw the same XyzUtil class pop up in two different companies, and both had been sourced from the same (not open source) third company repo, with the same bug that I ended up fixing twice.

I suspect this happens in other countries too, but I think elsewhere people make an effort to be less obvious about it. I get the impression copy paste programming isn't as looked down upon here as it is in the west.