This may be an employer-specific kind of a question. Within Alberta in Canada, I know and work with PTAs who have had PTA training, have been former nursing attendants, and a few who were foreign-trained Physiotherapists. Some places I've been, they only hired PTAs who graduated from certain colleges with the PTA training (ie. not former nursing attendants) but they also hired a few foreign-trained Physios.
I also had a few classmates who worked as PT Aides in some clinics while they were attending Physiotherapy school.
Hope this helps.