Initial part of the TAF applicability for planning

[RTN11]

You are completely misinterpreting the table.

1 states how to apply the initial part of the TAF, under which A states the initial TAF is only valid up to the first BECMG or similar, and B states that everything apart from the wind should be applied in full, as the gusts can be disregarded for planning purposes as per 2.

Section 2 then states how to apply the rest of the TAF, and clearly states that for all cases improvement shown by a BECMG is applicable from the end of the change. Therefore, for +/- one hour, in the example TAF you have given, for planning purposes the field can be taken as CAVOK from 1100z.

Many places issue 24 hour TAFs, what use would these be if there is fog in only the first two hours, and that has to be applied as planning minima for the entire period of the TAF?

This table is only designed as a quick reference. If you go to EASA ops and look at the acceptable means of compliance, it spells it out quite clearly:

AMC1 NCO.OP.160 Meteorological conditions

APPLICATION OF AERODROME FORECASTS (TAF & TREND) — AEROPLANES AND HELICOPTERS
Where a terminal area forecast (TAF) or meteorological aerodrome or aeronautical report (METAR)
with landing forecast (TREND) is used as forecast, the following criteria should be used:

(a) From the start of a TAF validity period up to the time of applicability of the first subsequent
'FM...' or 'BECMG' or, if no 'FM' or ‘BECMG' is given, up to the end of the validity period of the
TAF, the prevailing weather conditions forecast in the initial part of the TAF should be applied.

(b) From the time of observation of a METAR up to the time of applicability of the first subsequent
'FM...' or 'BECMG' or, if no 'FM' or ‘BECMG' is given, up to the end of the validity period of the
TREND, the prevailing weather conditions forecast in the METAR should be applied.

(c) Following FM (alone) or BECMG AT, any specified change should be applied from the time of the
change.

(d) Following BECMG (alone), BECMG FM, BECMG TL, BECMG FM TL:

(1) in the case of deterioration, any specified change should be applied from the start of the
change; and

(2) in the case of improvement, any specified change should be applied from the end of the
change.

(e) In a period indicated by TEMPO (alone), TEMPO FM, TEMPO TL, TEMPO FM TL, PROB30/40
(alone):

(1) deteriorations associated with persistent conditions in connection with e.g. haze, mist,
fog, dust/sandstorm, continuous precipitation should be applied;
Regulation (EU) 965/2012 on air operations Annex VII – Part-NCO
NCO.OP

(2) deteriorations associated with transient/showery conditions in connection with shortlived
weather phenomena, e.g. thunderstorms, showers may be ignored; and

(3) improvements should in all cases be disregarded.

(f) In a period indicated by PROB30/40 TEMPO:

(1) deteriorations may be disregarded; and

(2) improvements should be disregarded.

Note: Abbreviations used in the context of this AMC are as follows:
FM: from
BECMG: becoming
AT: at
TL: till
TEMPO: temporarily
PROB: probability