Well I've managed to come across yet another concept which could be considered "vague".
"If a model with a webway portal is in Reserves or Ongoing Reserves, then the model and any unit it has joined or is embarked upon has the Deep Strike special rule. This model, and his unit, will not scatter if arriving from Deep Strike Reserve."
So basically it only sais that the model with the WWP and the unit it joined won't scatter after Deep Striking, but it sais nothing about the Vehicle this unit is in. Would I be wrong to assume that this Vehicle (in this example a Raider) can still Deep Strike without scattering using a Haermonculus attached to a unit of Grotesque's that have this Raider as their Dedicated Transport?
(also if this is approved, must a transport be dedicated for it not to scatter when used as transport by a model with a WWP or can it be any vehicle that has the Transport rule in which the model with the WWP is placed?)