Now that more IT is entering the shop floor, many places are adopting some solutions (for diagnostics, data collection etc.) with more "computer" content than the past; for example all the predictive maintenance platforms big vendors are developing. Or you can concentrate on the "upper" levels, like SCADA, MES; of course working with these tools is not super CS rocket science, most of the time. You can start from positions more akin to programming, then work your way into process sensors technology, electrotechnics, etc. That's what I did.
Edit: System integrators as sibling says, I second that!
Controls aren't much different than other industries who rely on vendor product solutions either imo. You can talk to your SCADA vendor to see what their Historian / MES solution is and look at integrating that or develop a custom solution. Each obviously have pros/cons. What you might gain in rapid development using the Vendor provided solution your client will probably lose in steep licensing fees. Vendor solutions are typically set up in a way that anyone could configure them using only the manual and a few tutorials but giving any joe the ability to set up a system always has the drawback of the system being very "one size fits all" and customizing it to work in certain scenarios is difficult.
True! Hence my, "most of the time". I recently had to heavily customize a SCADA event engine with my plugins due to the particular requirements of the system; come to think of it, I might have as well rewritten the whole thing, but I had some "non-technological" limitations. :)
Edit: System integrators as sibling says, I second that!