The current 737 (all series) Vol 1 SP.16.5 states:-
“Wing Anti–Ice Operation–On the Ground
Wing anti–ice must be ON during all ground operations between engine start and takeoff, when icing conditions exist or are anticipated, unless the airplane is protected by the application of Type II or Type IV fluid in compliance with an approved ground de–icing program.
WARNING: Ground use of the wing anti–ice system is intended to complement, and not replace, ground de–icing/anti–icing and inspection procedures. Close inspection is still required to ensure that no frost, snow or ice is adhering to the wing, leading edge devices, stabilizer, control surfaces, or other critical airplane components at takeoff.”
I don’t think there is any grey area here. If your company has an SOP which is contrary to the above perhaps you should mention it to your fleet manager.
As to the background for the rule and the anomaly for non Type II or IV fluids, Boeing Aero magazine, issue No. 08, October 1999, had an article under 'Safety' on page 3 entitled “New, DEICING/ANTI-ICING FLUIDS”. In it, it discusses the development of new fluids, particularly Type IV and new problems to be addressed with longer hold-over times. One of the problems is the fact that the fluid can partially dry out before its hold over time has expired. Thus when it is supposed to shear off and leave a clean wing prior to lift off, in actual fact a thin film can be left on the surface of the wing which may affect the aerodynamic characteristics of the wing. Two of the situations where this was described were exposure to cold dry air and ground operation of heated wing leading edge systems.
In addition to the practical risks (above) there is an ongoing disagreement about standards which even after 6 years has still to be resolved:
“When AMS 1428 was issued, it was consistent with the ISO and AEA fluid standards. When AMS 1428 was revised (Oct 1998) to include standards for Type IV fluids, the SAE G-12 committee worked closely with the AEA ground de-icing working group to develop consistent standards. These standards could be used to revise the ISO standard and provide all operators with consistent standards for Types II, III, and IV fluids. However, the ISO standard has not yet been revised. Because of this situation and frequent changes to the SAE standard, Boeing has revised its AMMs and service letters to refer only to the latest revision of the SAE standard."
The bottom line is that you should not use wing A/I if you have been treated with Type II or IV fluids as per the current Vol 1. If you do, your hold over times will be reduced and you may also degrade the wing aerodynamic characteristics. If your airline has an SOP which is contrary to this, you should bring it to their attention.
S & L
(Edited for layout)