Well, to answer your question… when I play as Japan in this game I build ICs in China or Malaya in order to turn out ground units for taking India. I would rather spend 12 bucks on 3 mech inf than 18 bucks on tanks and the rest of my money goes towards building Navy to ward off the US. Your power lies in your airforce so what you really need (more than tanks) are just guys to lose, but plain infantry move so freaking slow.
India could use them to snag some territory that Japan might be neglecting, but I don’t really see how effective they could be for them.
For ANZAC they are a cheap alternative to tanks that can still reach every space in Australia. Pair 3 of them up with 4 fighters and taking out a small Japanese landing force should be easy.
The only way they could be useful to the US is if the US managed to take Korea and built a Major IC there. 10 of them could be very deadly in China.