As one who was once a member of a religious order, I can confirm the AE usage of 'Father' as a title for all priests, particularly as a spoken title when addressing them. Note that other titles may be used in more formal written English.
I find this definition cited by RE1 in posting #2, however, a little puzzling, however:
Main Entry: 1fa·ther
6: a priest of the regular clergy; broadly : priest —used especially as a titlehttp://www.merriam-webster.com/cgi-bin/dictio...
The issue here is the term "regular clergy," i.e., a member of a religious order. In this context "regular" is a technical term, and does not mean "normal." In English the distinction is made between the regular clergy (i.e., those who live according to a religious rule) and the secular clergy (those priests who are under the authority of a bishop). This definition would appear to suggest that the title "Father" is primarily for the regular clergy, and only more broadly for secular clergy. Historically, that is true (at one time, priests in the United States were addressed as Mr., (although this stemmed from the early Jesuit practice in the early American church)), but in contemporary usage, I have never heard anyone not use the title "Father" on the grounds that the priest was not a member of a religious order.