When a grantor or decedent transfers property into a trust which has, or which pours into another trust which has, more than one beneficiary or class of beneficiaries for GST purposes, and when the grantor or fiduciary allocates the grantor’s or decedent’s GST exemption for the benefit of one or more, but less than all, beneficiaries or classes of beneficiaries of such trust, or when the surviving spouse of the grantor or decedent, or such surviving spouse’s fiduciary, allocates the surviving spouse’s GST exemption for the benefit of one or more, but less than all, beneficiaries or classes of beneficiaries of such trust, and when the instrument creating the trust does not specifically prohibit a fiduciary from dividing such trust into separate share trusts, a fiduciary shall divide such trust into two or more separate share trusts, of equal or unequal value, in order to effectuate and carry out the allocation of the grantor’s or decedent’s GST exemption, or if applicable, the GST exemption of the surviving spouse of the grantor or decedent. Other terms and provisions of each such separate share trust shall, when taken together as a whole, be substantially identical to the original trust. In general, this section contemplates that a fiduciary will divide a single trust into two or more separate share trusts when such division may decrease or eliminate the amount of distributions from such single share trust that would otherwise be subject to the GST.