Once an application is received by Sydney, they enter info into their system. At some point later (currently it takes around 3 weeks) a sponsor gets AOR (acknowledgement of receipt) email to their inbox. At this point a sponsor or a PA can link an application to their online account. Either of them can do it. Here's the detailed explanation about that
https://www.canadavisa.com/canada-immigration-discussion-board/threads/how-to-link-an-application-to-cic-account-step-by-step-instruction.619724/
After AOR is issued, CIC starts processing sponsor's part of the application, i.e. they determine if a sponsor is eligible to be a sponsor. If the sponsor is approved, ECAS shows "Decision Made" under sponsor's part (on the left) and an email is sent to sponsor's inbox notifying of the decision.
At that time PA's part of an application starts and PA is requested to pass biometrics (this is done in the closest VAC) and medical exam for PA and all dependents listed in the application.
Once all that is done (or sometimes even before that) an application is transferred to a visa office responsible for PA's country. That also might be Mississauga which is considered to be the fastest one. A sponsor receives an email from CIC notifying of the transfer, and some time later ECAS starts showing "we started processing your application" under PA's part and a PA receives an email. This email is considered AOR2. Depending on your visa office you might have to wait for a few months before you can see this on ECAS.
And the final step is decision made under PA's part on ECAS and passport request.