I think it's a bit greedy to block all none-optus BYO devices for the wireless broadband plans, this information wasn't communicated to me when I took out my M2M braodband and it's not easily accessible, I actually only discovered this in a forum post from DAN_C after a couple hours of searching for the reason why my new 4G router wasn't working.
My new router does however work with Telstra all okay and so I've cancelled my optus plan and gone to them instead
@Dontbegreedy The Information is stated in the Critical Information Statement on the Website. You click on one of the devices, click view all plans and there is a link to the critical information statement.
These plans can only be used with the Optus-supplied modems provided with your 24-month Optus Wireless Broadband plan. Customers on a month-to-month plan will need to purchase a modem at an upfront cost, which will be advised at the time of purchase, in order to use this plan. The SIM supplied with the modem must not be removed from the modem and will not work in any other device."
You can buy a second hand device as long as it on the approved device list, you can buy the modem upfront or sign up for 24 months. If you sign up for 24 months $9 per month is credited towards the cost of the modem so if you leave after 6 months you just pay for the balance of the modem cost which would be $162.