Rod, have a good read of the policy and see exactly what is covered.
The aftermarket don't cover things considered to be wear & tear or serviceable parts
they are also generally a "mechanical failure" policy & use that term allot in their PDS.
Have a look at the page I have linked, you will have to know exactly which product
the dealer is selling you, They all have limits to the amount they will pay on any individual claim,
they have limits for types of failures, (some have limits of $4000 for engine, $2000 transmission, $1500 electrical components...etc...
if you pay $1700 for policy then $100 excess on claim & only have say $2000 limit on transmission it's not going to be worth buying for that alone)
they mostly have an excess to be paid on each claim,
they can ask you to contribute towards repairs if they consider wear to be a factor in the breakdown
& they also have total claim limits.
As I wrote, make certain you know exactly which policy you are getting
& see what is covered & what is not covered.
http://www.swanninsurance.com.au/docs/warranty.pdf
Dealer cost on those warranties is around $600 from memory so they use them to add gross into the deal
& quite often they will throw them at you for nothing to get a deal, saying "I have just given you an extra $1,700"
If it was me, I would steer away from the car entirely because of it's well known expensive repair problems.