Not a chance if the ballast is inside too. The 150W rating simply means the heat loss of the fixture with 150W being dissipated inside it will not cause a fire. It doesn't grant any concessions to keeping the temperature low. The electronics in the ballast will likely choke in short order.
Yes, the fixture will be perfectly fine. The CFL bulb, maybe, maybe not. It depends on many details that we don't know. It's high risk that it would get too hot.
Given that they're now about $10 each, why not try one to see how it goes?
Just mounting a a CFL upside down significantly reduces its life due to heat rising and heating the electronics. The mounting position is probably more important than the fixture. A 23 watt CFL will last longer than a 42 watt.
I have had terrible experiences using CFLs inside the totally enclosed fixture in my living room with typical life less than a year. Other better ventilated fixtures using the same batch of bulbs have been going strong for several year.
