"'does not apply to a change of contractor if there is no concommitant transfer from one undertaking to the other of significant tangible or intangible assets or taking over by the new employer of a major part of the workforce, in terms of their numbers and skills, assigned by the transferor to the performance of the contract. The decisive criterion for establishing the existence of a transfer within the meaning of the Directive is whether the entity in question retains its identity. The term 'entity' refers to an organised grouping of persons and assets facilitating the exercise of an economic activity which pursues a specific objective. The mere fact that the service provided by the old and new contractor is similar does not support the conclusion that an economic entity has been transferred. An entity cannot be reduced to the activity entrusted to it ...