The appendix in the back of UL 498 that details hospital-grade plugs does not list NEMA 1-15 as being approvable as a hospital-grade component. I believe part of the reason stems from the fact that part of the criteria for achieving hospital-grade status involves protecting the ground connection, which automatically disqualifies the NEMA 1-15 styles. UL 60601 does in fact have provisions for Class II equipment, but these requirements are substantially different from Class I requirements. The same can be said regarding the construction of Class I and Class II plugs in general, which also does not lend itself to adapting the 1-15 plugs to Class I hospital-grade requirements. At this time, I cannot say how plugs for Class II devices are handled by the agencies and equipment manufacturers. It is almost certain that they are using either standard NEMA 1-15 plugs or that somebody is making a more durable version that is being allowed for use on such equipment.  For an answer to this question, we would recommend you speak to a UL engineer whose area of product expertise is medical equipment approval.

I am quite sure a NEMA 1-15 could be developed to meet the requirements of a Class II plug and the requirements of UL 60601, but it could not be designated hospital grade or marked with a Green Dot without a standard change. I would think that the construction of such a plug would need to follow the double insulation criteria for Class II items, as well as have a beefier, more durable construction than most NEMA 1-15 styles on the market (similar to Class I hospital-grade plugs).