There is corruption everywhere (though obviously not uniformly distributed). It requires active, dynamic efforts to counteract. If you don't see some evidence of successful prosecution, that itself is informative.

The corruption would be if this is not punished. By for example Newag getting a massive fine.

It's a criminal case. Money is not enough.

I think that there are two separate issues here:

1. train manufacturer bricking trains - malice and monopolism as you say

2. prosecutors failing to bring court cases and convictions for train manufacturers - incompetence or more likely corruption.

It might be different if you manage to get your competitor fined 500k

500k is fraction of train cost. Eventual fine, to work properly, would need to be in hundreds of millions.

I think the 500k was a reference to the fine the third-party service company (SPS Mieczkowski) had to pay due to the failure that it now turns out was intentionally caused by Newag.