Home sharing and NAT

Hello)

Noticed strange thing with Home Sharing. According to Apple it works only in local network, but in my case I could see my iTunes library even on Mac at my work and my home Mac doesnt have direct (or "white") IP. I'm able to play music/video from my home iTunes library, etc. I was thinking about VPN to do such thing, but now I see that it works without any VPN! And its awesome. But I have a question - is it normal? Any of you also could connect to home shared library from the internet, not local network?

And another thing: all this works on mac, but not iPhone/iPad. Even with VPN I couldnt connect Home shared library( Is there any way to do this?

Thanks a lot)