do large mining operations network their miners so that they don't overlap their hashes

Interestingly, it's hypothesized that Satoshi did this:

He suggested that Satoshi had access to 58 machines for mining, so to avoid checking the same nonce twice he gave each machine a different id, which was stamped in the LSB of the nonce.

https://bitslog.wordpress.com/2013/09/03/new-mystery-about-s...