Vinyl composition tile (VCT) is commonly approved as a restroom floor surface, so vinyl plank flooring should be acceptable as well. However, it depends on the vinyl plank flooring selected.
There are two types of vinyl flooring per ASTM F1700: Type A (smooth surface) and Type B (embossed surface). The Type B flooring would not be permissible, since the embossing process leaves grooves and textures (commonly a wood grain pattern) that would not comply with the "smooth" part of IBC Section 1209.2.1.
As for the "nonabsorbent" characteristic in IBC Section 1209.2.1, vinyl does not absorb liquid water (as a matter of fact, sheet vinyl will act as a vapor retarder, so even water vapor is difficult to pass through vinyl flooring). As part of the ASTM F1700 requirements, vinyl flooring is required to be resistant to many household chemicals with only a slight change. However, to improve its water resistance, I suggest planks with interlocking tongue-and-groove edges.
And for the "hard" part of IBC Section 1209.2.1? Well, it depends on your definition of hard. ASTM F1700 does not specify a "hardness" characteristic for vinyl flooring; thus, nearly all vinyl flooring manufacturers do not mention hardness for the vinyl tile. However, ASTM F1700 does have a "Residual Indentation" characteristic tested per ASTM F1914. The test places a 140 lb load of a certain area (4.5 mm diameter) on the material for a specified duration (10 minutes). The load is removed and a measurement is taken one hour after the load is removed for material recovery. The thickness at the indentation is measured and compared to the thickness before the load is applied. The indentation cannot be more than 8% of the overall thickness. I would think a product with that kind of resistance would be considered "hard."