C1 can be achieved (I did it on 360 hours). C2 is academic level of language proficiency -- you have to either deliberately study for the difficult exam or get an university degree in German. Most of the Germans won't be able to pass a C2 test.
When a company sets C2 as a requirement, it can be interpreted as "must have a degree from German University".
When a company sets C2 as a requirement, it can be interpreted as "must have a degree from German University".