Cool bulbs into a min 90C fixture with 60C wiring
That's not a good workaround.  Recessed Insulation Contact (IC) lighting fixtures have a target temperature of 90ºC in the junction box.  Kinda crazy, but that's what it is. See NEMA Bulletin #92 (December 2005) which reads:


  When the dwelling’s existing wiring is rated 60ºC, install a junction
  box approximately 18 inches away from the newly installed lighting
  fixture and then run Type NM-B from the junction box to the fixture.


Installing the energy efficient bulb will not meet code.  You'll be fine.  But how are you going to prevent the next owner from sticking a hefty bulb in there?

An alternative is to take that fixture back, find something with a GU-24 socket, and hope the vendor was smart enough to realize that GU-24 means lower heat.