Filing a patent application with USPTO, and the same day filing the same patent application internationally (PCT); does it entitle to a fast response? I've seen a case receiving the first Office Action from USPTO within 3 months, and it was not under the TrackOne program.
No. You have just stumbled on a lucky case or two. There is a way that a PCT application can help get a faster response on a U.S. application. If a non-provisional U.S. application and a PCT application are both filed at the 12 month point after a provisional they both get priority from, you can expect a search report from the ISA of the PCT six months later. That will be 18 months after the provisional filing. If it is positive, you can file to have the US case move faster by using a - free - Patent Prosecution Highway request. It is not as fast as track one.