This was an IT failure, not a Windows failure.
Quite correct! The CAD system is not a Windows only platform! While not wanting to defend Microsoft or Windows and their appalling approach to security, there is nothing to be gained by simplifying this incident to a Windows flaw.
Frankly for something critical like this I wouldn't use any consumer OS. I would use a hardened real time OS or similar.
But of course the ability of management* to easily pull data in and out of Excel is considered more important than the reliability and ease of maintenance of the system.
Properly designed and hardened, a good back end system can maintain it's integrity without risk. The real risk is that any data extracted to insecure systems becomes insecure also. If the front end interface is properly thought out and flexible enough to meet routine needs, then you have to question why there is a need for extraction onto unmanaged and insecure excel spreadsheets.
* Every public service in NSW is way over burdened with dickheads in Sydney getting six figures to molest data instead of allowing the workers to actually do their jobs.
And there in lies the problem! Contracts awarded to political mates rather than via merit via open and compliant tenders!
There is an election in a few weeks time to tell the incumbents and their stacked public service hierarchy how we feel about their management and spending performance.