The Australian Classification Board has jsut released the new overall guidelines for games classifiction, including the new R18+ rating, to be introduced early next year.
You can have a look at the entire document here, but the relevant section is pasted below:
R 18+ - RESTRICTED
The impact of material classified R 18+ should not exceed high.
Note: Material classified R 18+ is legally restricted to adults. Some material classified R 18+
may be offensive to sections of the adult community.
There are virtually no restrictions on the treatment of themes.
Violence is permitted. High impact violence that is, in context, frequently gratuitous, exploitative and offensive to a reasonable adult will not be permitted.
Actual sexual violence is not permitted.
Implied sexual violence that is visually depicted, interactive, not justified by context or related to incentives or rewards is not permitted.
Depictions of actual sexual activity are not permitted.
Depictions of simulated sexual activity may be permitted.
Depictions of simulated sexual activity that are explicit and realistic are not permitted.
There are virtually no restrictions on language.
Drug use is permitted.
Drug use related to incentives and rewards is not permitted.
Interactive illicit or proscribed drug use that is detailed and realistic is not permitted.
Nudity is permitted.
It could be argued that this isn't that different from the previous MA15 rating, as the issues of, for instance, drug use for reward is still a no-no. So, effectively, random and meaningless drug abuse is A-okay in a game, so long as it's not realistic.
The guidelines on sexual activity or similarly vague, and actually make it sound like games such as Mass Effect 3 (where I'd say the sex is far from 'implied') would now become R-rated. And speaking of sex, where would this leave games such as the new Tomb Raider, or even Hitman: Absolution. There may not be any actual sexual violence in these titles, but it is certainly implied.
And then, of course, the guideline still takes the stance that interactive violence is more impactful. "...as a general rule computer games may have a higher impact than similarly themed depictions of the classifiable elements in film, and therefore greater potential for harm or detriment..."
At the end of the day, though, these are just guidelines, and their interpretation is what's going to have the most impact. We can only hope the people enforcing this new code are as game literate as possible, otherwise we're not really getting anything new at all.