1) You won't hear anything from Mississauga--not even confirmation of receipt--until they have actually finished processing your sponsorship portion altogether and have forwarded your file to Buffalo. Usually takes them 30-40 days to do that and send you a letter in the mail telling you what their decision was. You won't be getting an email from them.
2) Only AFTER they have finished processing and have activated your eCAS, will you be able to check your status online. You would need to go here: https://services3.cic.gc.ca/ecas/?app=ecas&lang=en and enter in the sponsor's personal information along with your receipt number. BUT there have been cases where either they were very slow activating eCAS, or never bothered. So if you don't see anything even after the 35 day mark, don't worry; it happens. I know some people call CIC's call center when it's been more than 30 days and try to figure out what their status is that way, too.
3) Abbreviations:
AOR = Acknowledgment of Receipt, the letter Buffalo will eventually mail or email to you telling you that they have your file, and giving you your immigration file number. It could take them a month or more, after your sponsorship has been approved, to send this.
PPR = Passport Request. When your processing is done, you are approved, and they are ready to issue your PR visa, they will send you a PPR letter (could be by email, regular mail, or both) asking you for your passport along with instructions on how to do this and whether they also need photos or not. PPR = you're done! All that's left after that is to land.
eCAS = CIC's online "Client Application Status" system, for checking the status of your Canadian immigration or citizenship application online. Not always updated promptly. Not usually detailed in any way. Sometimes very unreliable. Some visa offices keep it updated, some don't.
4) The 11 month timeline for Buffalo on the website is assumed to be representative of 80% of the cases. It is not uncommon for straightforward cases to be processed much faster than that. But a lot of this presumably depends on how backlogged Buffalo is, whether they have to request additional documents from you, how long it takes for your background check to be completed, etc. Many, many factors. There's no real "accurate" or iron clad way to say how long it will take, unfortunately.
Edit: Forgot that you also asked what eCAS was.
