If you know that you have been accepted because you received an email, then that's the "letter" that it mentioned on CIC website when you log in. Don't expect anything else. The first stage is done, your file has been transferred to Buenos Aires, and now... you wait! there is nothing else to do.
Ecas doesn't have much information. For now, it will stay the same. You might see "medicals have been received", but not always. It doesn't show when your file is opened in Buenos Aires. Most of the times it's not updated, so don't obsess too much about it. You can sit back and relax... when Buenos Aires opens your file and start working on it, they might send an email to your wife ( as for stage 2, all communications go to the applicant, unless you have filled out the "use of representative" form) asking for more documents or her passport. BA is currently listed at 15 months ( see here http://www.cic.gc.ca/english/information/times/perm/fc-spouses.asp#west), so don't expect to hear anything about your file for probably another 6 to 8 months.
Good luck,
Sweden