No, I never found a way to do that.
The PICAXE updates the internal port direction bits every command so any attempt to poke to the underlying hardware registers is quickly thwarted. For the 18X it's necessary to keep data which says what the direction bits must be to allow I2C operations and, luckily for us, the way it was implemented is that this $AE shadow register is what the Output Pin directions are written from.
There's no need to make the Input Pins' directions programmable, so no shadow register availabe for that.