>>>>>> I don't have access to a FAR/AIM at this time,
You can find the Regulations on the net at:
http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?&c=ecfr&tpl=/ecfrbrowse/Title14/14tab_02.tpl
The reason I suggested reading the regs is because this question comes up pretty often, and it almost always gets at least 3 different answers. Anyway, here's the relevant regs
ATP:
§ 61.39 Prerequisites for practical tests.
(b) Notwithstanding the provisions of paragraphs (a)(1) and (2) of this section, an applicant for an airline transport pilot certificate or an additional rating to an airline transport certificate may take the practical test for that certificate or rating with an expired knowledge test report, provided that the applicant:
(1) Is employed as a flight crewmember by a certificate holder under part 121, 125, or 135 of this chapter at the time of the practical test and has satisfactorily accomplished that operator's approved—
(i) Pilot in command aircraft qualification training program that is appropriate to the certificate and rating sought; and
(ii) Qualification training requirements appropriate to the certificate and rating sought;
Flight Engineer:
§ 63.35(1) The applicant—
(i) Within the period ending 24 calendar months after the month in which the applicant passed the written test, is employed as a flight crewmember or mechanic by a U.S. air carrier or commercial operator operating either under part 121 or as a commuter air carrier under part 135 (as defined in part 298 of this title) and is employed by such a certificate holder at the time of the flight test;
(ii) If employed as a flight crewmember, has completed initial training, and, if appropriate, transition or upgrade training; and
(iii) Meets the recurrent training requirements of the applicable part or, for mechanics, meets the recency of experience requirements of part 65; or