Cenvat credit on invoice issued to sister unit

A" is an excise registered unit, it has another unit "B",

1.there are invoices issued to B, as buyer/consignee, however  excise registration number mentioned is of A, who can avail cenvat credit on these invoices, goods came to the premises of A, 

2. There is one invoice, on which goods came to A, but address is of B, but does not have excise registration no of A or B, it has TIN no but that is of neither A nor B, who can avail credit on this invoice?