That one I can definitely help with.

Physiotherapy Business Australia is the private practice special group of the Australian Physiotherapy Association.

www.physiotherapy.asn.au/pba

PBA is the APA's expert reference group on private practice matters and thus it is involved in the wide range of activities undertaken by the APA. This includes:
Working on private practice related advocacy (Veterans affairs, health insurance, workers compensation).
A quarterly magazine focused on the business of physiotherapy
A monthly email newsflash keeping people up to date with private practice issues
Annual research on market rates

Practice owners can also get access to:
An industrial relations telephone support line
1800 advice line
Business related hot topics and advice sheets
Marketing solutions (Directory for referrers, searchable listing in Medical Director & eMIMS software, searchable listing on Australia’s No. 1 health consumer website. We've also introduced late last year a service that delivers fortnightly customised brochures, signs and marketing materials via email.

As for other groups, I'm not even sure that any other group still exists. They certainly don’t have a seat at any of the health industry advisory panels for organisations such as Medicare, DVA, Health Insurance Association, Workers Compensation Authorities, Australian Council of Physiotherapy Registration Authorities, Health Professionals Council of Australia. They haven't done any submissions for fees that we're aware of (all the recent increases - including the current DVA increases and the NSW Workcover increase that should be published tomorrow - have been done by the APA with PBA's support as expert reference). They haven't contributed to any major reviews lately (Review of the Privacy act, Trade practices act, productivity commission review of health workforce). I haven't heard much about splinter groups in the last 2 years and I suspect that many members of splinter groups retain thier PBA membership anyway.