Telstra's official tethering policy
Telstra's Terms of Service (ToS), available at http://telstra.com.au/customer-terms/home-family/telstra-mobile/, do not address any limits on use of your data plan in regards to tethering.
Telstra's wireless support FAQ's, located at http://help.telstra.com/app/answers/detail/a_id/17370/c/1986/kw/tethering/r_id/130958, defines Telstra's stance on tethering as
Currently Telstra allows tethering, it will use the same data as your monthly data allowance.
Telstra's Terms of Service (ToS), available at http://telstra.com.au/customer-terms/home-family/telstra-mobile/, do not address any limits on use of your data plan in regards to tethering.
Telstra's wireless support FAQ's, located at http://help.telstra.com/app/answers/detail/a_id/17370/c/1986/kw/tethering/r_id/130958, defines Telstra's stance on tethering as
Can I use my mobile as a modem, to access the internet?
Most Next G™ mobiles can also be used as a wireless broadband connection. To see if yours can, please check your phone manual...Data charges apply – we recommend buying a browsing pack to minimise your data costs.
Currently Telstra allows tethering, it will use the same data as your monthly data allowance.