Concrete ties brought about a new kind of track defect. On curves, it isn't uncommon for the concrete to deteriorate underneath the rail base on the field side of a curve. This allows the rail to tilt under a train. With modern heavy (as in tall rail), this outward tilt can be enough to create a wide gauge condition. On wood ties, it is more common for the base of the rail and tie plate to shift towards wide gauge.

I believe the FRA is having to create new standards for concrete ties. Didn't Amtrak derail in the Columbia Gorge a few years back due to this?

I have seen a variety of rail securement schemes being used on concrete ties. The fasteners not only have to hold gauge, but also have to act as anchors to keep welded rail in the correct state.

If you look on mainline track, you will notice that the concrete ties on sharper curves are actually marked as having gauge greater than 56 1/2"