Confusion regarding Explanation 4A of Sec 43(1)

I have a confusion regarding Explanation 4A of Sec 43(1) of Income Tax Act

My problem is as follows,

 X  Sold a Plant to  Y on 1.6.2008 at 2,00,000.

 W.D.V on the date of transfer by  X to Y is 1,50,000. In the Books of Y  W.D.V of  the relevant  Block (Plant @ 15% dep)    as on 1.4.2008 was 3,00,000. Y  treated  the Plant as follows:

                                                                              In the Books of  Y

         W.D.V of the relevant Block on 1.4.2008                                  3,00,000

           Add: Additions during the year 2008-2009                            Rs. 2,00,000

                                                                                                                          5,00,000

           Less: Sale proceeds                                                                              nil      .

                                                                                                                         5,00,000

            Depreciation @ 15%                                                                           75,000  .

               W.D.V as on 31.3.2009                                                                 4,25,000

             Add: Additions during the year 2009-2010                                     50,000  .

                                                                                                                          4,75,000

            Less: Sale Proceeds                                                                            nil         .

                                                                                                                          4,75,000

            Less: Depreciation @ 15%                                                                 71,250   .

                                             W.D.V as on 31.3.2010                                   4,03,750   .

Now on 1.8.2010 the Plant which was acquired by Y from X was LEASED back to X  by  Y.

Vide Explanation 4A of Sec 43(1) the actual cost of the asset for the purpose of depreciation in the hands of  Y will be the W.D.V on the date of transfer by  X  to Y i.e, 1,50,000.

My question is whether the above calculation of the depreciation will be recomputed and assessment order of the

P.Y 2008-2009 and 2009-2010 will be rectified u/s 154? Please show the the computation of the depreciation and W.D.V of the relevant Block during the P. Y 2010-11 in the Books of Y. (assume there is no purchase or sale of plant in 2010-2011)