Wonder Boy,
There are minimum legislative requirements determining when LVP's will be introduced, particularly visibility falling to 1500m (CAT I) or below and cloud ceiling of 200' or less. Obviously for CAT II or III approaches the vis minima are more restrictive (800m or lower) but the cloud ceiling minima are more difficult to stipulate as a lot of the time different minima could apply to different aircrew flying the same approach depending on crew qualifications and airborne/ground equipment available.
Also, there are different methods of implementation (and different names for the various methods!) at different airfields, and will be detailed in that airfield's ATC instructions or MATS II. However, each method will have to have been fully audited and approved by the relevant regulator before it can be used.
I think what you are referring to here may be an airfield where the runway and vehicle holding points are far enough from the runway centreline that they provide the equivalent of CAT II/III protection in all weather conditions, and the vehicle holding/access points have some method of positive control that enables their use in poor or marginal conditions without a requirement for them to be physically blocked off (i.e the use of traffic lights that are switchable from the tower, for example).
Provided that all of the relevant holding points and airfield access points are visible from the tower and the controller can therefore maintain positive control of the manoeuvring area, thereby protecting the ILS sensitive and critical areas, then there is no reason why CAT II ops cannot proceed without the actual declaration of LVP's. Obviously there will have to be some form of airfield procedures enforced to ensure the required safeguarding, but that does not necessarily equate to full LVP's.
An airfield at which I previously worked got around the problem to which you refer by having various stages of LVP's depending on the conditions which prevailed or were forecast. With reference specifically to the scenario you mentioned, where the cloud ceiling fell to 200' or below (either at the 'field or affecting the approach) but the visibility remained good below cloud, the procedures adopted were known as "LVP Cloud", and provided the required safeguarding for the approach aids without having the airfield surface traffic grind to a halt unnecessarily! It meant that it was (almost) business as usual on the ground, while the airborne crews were satisfied that they had the minimum equipment protection in place to guarantee a safe approach.