Would it be possible that the crew was only able to communicate through ACARS, hence the 4 minute communication? From what I've read on ACARS sites it's not just limited to automated technical info:
eg:
N156DL B767-3P6[ER] 25354/406 1506 PQ-DK [A40-GR]
Delta Airlines USA DL0124 Atlanta GA USA-Brussels Belgium
Using Ground Station E Amsterdam (AMS) .Message No. M57A
Message Type 80 POSITION REPORT
IN RANGE TYPE REPORT/23 Atlanta Hartsfield Int. Airport GA USA / Brussels Airport Belgium .N156DL
/DESTINATION STATION: Brussels Airport Belgium /ESTIMATED RAMP TIME 0725/CHAIR /MNR /PASSENGER AGENT REQUIRED TO MEET FLIGHT N/MEDICAL
N/SECURITY ASSISTANCE REQUIRED N/LANGUAGE INTERPRETER REQUIRED N/LAVATORY SERVICING Y/CABIN SERVICING REQUIRED Y
or:
9V-SPA B747-412 26550/1040 ER-AF
Singapore Airlines SQ0308 Singapore Singapore-London Heathrow United Kingdom
Using Ground Station X Birmingham (BHX) .Message No. 203A
Message Type H1 CENTRAL FAULT DISPLAY (Up/Downlink)
#T2B/ London Heathrow Airport UK KKSQ London Heathrow Airport UK KDSQ. ENGINEER NEEDED
PASSENGER MR REYNOLDS (14K) HAS DROPPED HIS NEW DIGITAL CAMERA REMOTE CONTROL IN NARROW SLOT NEAR ARMREST.
SUSPECTED TO BE INSIDE AREA UNDER SEAT.
(source:
Vliegtuigen en Communicatie:Acars Wacars Analyser - Stego)