Yes, they are available for download.

Go to the Missions Download page.

Select the Mission you want.

Click on the links for Part One and Part Two in the grey "Download" box on the right. (Directly above the "Get Adobe Redaer" link.)

Also -- I don't understand what you mean by "They won't be official." While you won't be able to send in feedback to effect future campaign adventures, the runs will count fully from the perspective of the characters. (IE - They'll get debriefing logs, contacts, nuyen, karma, etc.)

Well, he mentioned Parliament of Thieves, so I don't think so. However, the SRM00 & SRM01 adventures are all available from the archive page at the bottom of the above linked web site.

Here's the direct link to the SR3 scenario archive.

While an SR4 character can't go back and play an SR3 adventure, if a GM wants to first build up karma for his players' characters, he could run them through all 13 SR3 adventures, then do karma rollover for new characters in the SR4 campaign.