Can an opamp designated as a single supply opamp be driven from +/- dual supplies as long as it is within the VDD - VSS range? I'm looking at this particular opamp from Microchip.
A voltage is a difference in potential measured between two points. Traditionally, we label ground as 0V and measure from there, but you can choose any point on your circuit to call zero. If you choose your negative supply, then just by changing your labels, it's back to a single supply! So yes, it is always possible.
That said, take a bit of care when looking at the datasheet. If the datasheet has been written with single supply in mind, then some of the voltages given will be referenced to the negative supply. So if it says "max 3V" somewhere, it now means "max 3V more than negative supply rail".
An op-amp has basically 5 pins; Input+, Input-, Output, +Vsupply and -Vsupply.
It doesn't know anything about mid rails until you connect signals to its inputs. That mid rail is usually set about half-way between the two supply voltages. This makes the the voltage you connect to -Vsupply more negative than mid rail but it needn't be absolutely negative because midrail needn't be 0V - it can be positive and -Vsupply can be 0V or earth.
As others said, it doesn't matter. I just wanted to add an additional info: the opamps that are branded as "single supply" usually indicate opamps that have their input common-mode range including the negative supply (ground), but not including the positive supply. This way, even with a single supply, you can have measurements close to the ground potential (which is often required). That is why they are called like that.
The opamps that have the common-mode range including both the negative and the positive supply voltages are called "rail-to-rail input" opamps.