@ninja as long as you have degree in nursing there is no reason why you would not be registered. I have recently received my Australian nursing registration in principals its children's nursing degree. If you have a diploma then yes you would have difficulty obtaining registration.
What visa option are you intending to take. If you, like myself are planning to go via the visa 189, this is skilled migrant visa which gives you permanent residency. You do not necessarily have to have 3 years working experience. You gain points for 3-5 years experience but you do NOT have to them if you are able to make the points up somewhere else which will most likely be in the English criteria. You are required to have a skilled assessment carried out by the agency ANMAC who provide evidence of your skill, they only require you to have been qualified and working for at least 3 months full time or equivalent part time.
It is wirth you going in to the immigration website and finding the visa option you are wanting (I'm guessing you want 189) they give you a points calculator. If I can achieve maximum points on the English section (which I am working on) I have a total of 65 points out of the required 60 and I don't have 3 years post grad experience.
I hope this helps. I think you have a bit of research to do but I think there is nothing starting the process now.