This is more of a public service announcement, not sure how long this has been the case (as I haven't been overseas for a while) but I'm on one of the 365 day Kogan mobile plans and in Hong Kong at the moment and I'm able to receive texts which is surprising.
It's been helpful when asked to verify payments for things sending texts to my AU mobile number. Very cool imo!
(I don't think I'll be charged extra as it's a prepaid service anyway?)
Edit: here's a screenshot showing the message and the roaming sign http://imgur.com/a/pv4rssa
Related to International Roaming? It's indeed very useful.