When ever there is an extended power outage at a facility like this, tankers show up. I would not be surprised if there are contracts with Suncor distribution to have a steady flow of tankers supplying fuel to the facility. There are several fuel distribution hubs throughout the DFW area that supply the local markets including two major airports.
That's a big assumption, and precisely why the tanks are on site. If snowpocalypse events make roads unsafe to drive, those tankers might not be there. There's always a way to think about how something else could go wrong. At some point, you just have to say it is good enough for the money willing to be spent.