I work in an industrial plant and we have one network(physical wire) that us used for both office usage and for process systems. The office computers are only used for typical office needs but occasionally do connect to the process computers to obtain information from a sql server or for some other purpose. 

A new initiative is in the works and is rolling down hill from corporate and that is to standardize how the the computers are used at work and they would be severely locked down and only a standard set of applications will be allowed to execute.

one of the requirements is to also have non office computers isolated from the company domain. our non-office computers are a mix of Man-Machine interfaces and sql-servers all running software that non standard.

My question is, how can we divorce the control systems computers from the company domain but still have access to the servers from the company domain.

thanks