you should start with the BTS Product Description.
to move traffic, you can adjust the TRX parameter called “TRX_PREF_MARK’. A high value will make the TRX more “desireable” from CS traffic point of view.
At least one TRX should be = 0, in order to activate PS service in the cell. (only TRX pref mark = 0 are able to carry PS traffic)