In general, the disease risk of toilet seats is overrated, but you probably can get Ebola from a toilet seat.
The risk is not so much the seat itself as the whole bathroom. But not just any bathroom. The risk would come from a bathroom that an Ebola victim in an infectious phase has recently used.
The field hospitals run by Doctors Without Borders in Africa are laid out so that patients who definitely have Ebola never share toilet facilities with staff members or with patients who are only “possible” cases.
Ebola victims often lose control of their bowels and excrete copious amounts of diarrhea. They also vomit heavily. Those liquids are highly infectious. Touching them and then touching one’s eye or mouth or inside the nose could transmit the disease. Urine also carries some risk, but viral loads in urine are not nearly as high as those in vomit and feces.
For workers in Ebola field hospitals, one of the riskiest acts is touching their boots or shoe covers. The Doctors Without Borders disrobing protocol calls from them to slosh their feet in a bath of chlorinated water and then remove their boots with a bootjack, so as to never touch them with their hands.
In modern buildings, toilets that flush loudly and powerfully are a risk in themselves. The flushing create a mist of droplets that splash onto the face and hands or may contaminate stall surfaces.
The Aussies are not having any of this. Amnesty International can go fly a kite.