Absolutely, and if I find out that it was, I'll personally go up to Ohio and B-slap the idiot that approved such a connection. It is NOT common practice to connect a control system to the internet, though there can be specific dial-up links for maintenance/analysis (which are hopefully protected by unusually long multi-character passwords and such).
You obviously have better insights into that SCADA computer, which I appreciate your sharing.
I know of a lot of smart metering in substations that is polled by using either dial-up, the internet, or some LAN.
Alot of equipment vendors brag about how they can call up their smart control devices and do a diagnostic with their office computers. It wouldn't take much to contaminate such equipment with a virus if one was sloppy. Remember that the Blaster virus cause computers to reboot until they frooze up.
In the good old days, SCADA RTUs would have been connected to the SCADA main station either via dedicated mircowave, dedicated radio, leased copper phone line, or dedicated utility owned fiber optic. That was the "good old days" now low bid is often considered. (Yes, radio isn't as secure as it use to be considered with the ME Mag Pringles directional antenna.)
Earlier today I read a report based on a Commonwealth Associates, Inc. power flow model of the grid. They started with the summer peak load standard load flow, then did some modifications to take off line certain power plants, then changed some Canadian utilities from exporters to importers of power. Then they walked throught the NERC sequence of events, transmission line outage by outage to see if that would cause more transmission lines to exceed emergency ratings.
They couldn't model the exact sequence of events. After a number of lines had tripped out, they started to be able to come close to actual conditions for a while. Although there is an interesting discussion in the report at one place that the lines exceeded their normal maximum ratings, but that dispatchers at this point should have switched over to using the transmission line's emergency rating but some lines that triped off according to their models were over normal max rating but not emergency ratings. The also found that a lot of 138 kV lines seemed very heavily loaded at the beginning of the grid collapse. Toward the end when things started to really happen fast, they couldn't get their power flow model to converge to a solution so they think it will take dynamic modeling to really track things.