Yes, they made an exception for Japan although you never “Build” an IC there. Also they made the funny rule about only scrambling planes from an island, and Japan is able to defend herself while New Guniea (I think?) is split into two TT. There are a few contrivances on the map like that.
If you are not playing by the OOB rules, then you can scramble from any TT, with an airbase, bordering a SZ.