I'm running a SCADA application (my own program) on Linux. It communicates with 15 PLCs, tens of barcode readers, 6 inspection cameras, and many printers. That machine also run Apache WEBserver for HMI and SQLite for database and archiving. The machine has been installed 18 months ago and it is running 24X7, real-time. I never rebooted the Linux server.
To conclude, I can't recommend a SCADA application but I can say that Linux is an excellent platform for robust applications.
It is very dynamic and we run the server on VMS and linux. The client is used on linux and windows.
First we used it for simple hmi's with labels, buttons, tables and xy graphics.
But now pvbrowser is capable of useing SVG graphics. We now are also useing autocad drawings and convert them to SVG. The SVG's are then animated from our simulation models and our process variables.
Yes, for the past decade too. There are servers running in major paper companies, oil and gas, metals and a full system based on Linux for electrical utilities in China. Basically a replacement for DCS/PLC and includes the HMI via X-Windows.