Yes.

I installed a fixture that a customer had selected and purchased that required a "B" lamp as shown in the chart. Note that "C' lamps also are in the 15 diameter. The numbers refer to the major diameter in 1/8 of an inch -- thus a 15 is 1 7/8" diameter. Your A15 fixture might not accommodate the typically longer C15 lamp-- but it also might do so. Finding an LED suitable for enclosed that will physically fit may prove challenging. My assumption is that such an LED will have a larger heat sink. Definitely inquire of Switch and they may have suggestions that will be helpful.

The 60 watt limit on the fixtures is due to 2 things: the electrical current draw and the heat produced. No 13 or 16 watt LED light will draw excessive current (quite the opposite!) nor will it produce as much heat as an incandescent light. Replace with LED with a clear conscience and no worry. I have LED spotlights in my recessed light fixtures in my kitchen and no problems - and much better visibility!

LED lights on a house circuit require a "driver" to change 120 volt AC to low voltage DC and protect the LEDs from fluctuations in voltage and current that can cause the diodes to vary in output or degrade faster due to high temperatures within the diodes. This is especially important inside of a small recessed light fixture. In an integral LED recessed fixture the "driver" is a small brick-like thing in the housing external from the rest of the fixture with a wire to the "light engine" which is the diode array sandwiched between a lens and a cast metal heatsink. The life of such a light is usually rated at 50,000 hours ... whatever that means. An LED lamp (commonly called a "light bulb") is similar but has an internal miniaturized driver in its base connected to an array of diodes behind a frosted lens. Some have a metal surround with holes that acts as a heat sink but more commonly they rely on the wide spacing of the diodes and the closeness of the lamp to the fixture opening to reduce the chance of overheating. These lamps usually have a rated life of 25,000 hours but often fail much sooner. If you pay $15 for a PAR 20 LED lamp and $24 for the appropriate dimmer it might take a long time to break even unless you're putting the PAR 20's in existing 5" fixtures.