OK this is how we do it in the big city. BECAREFUL as this is not for everyone
If you take a good sledge hammer and place a few good wacks (4-7) you can actually split the tub in half.
A lot of the old cast Iron tubs I remove on 5 story walk ups we split this way
The key is knowing the following.
1- Cast Iron will crack into many particles and it is also like shrapnel with the baked on enamel. This stuff can cut you like a razor so wear eye protection and long sleeve shirts.
2-The pieces shoot all over the place making clean up a slight mess.
You maybe better off disconnecting the tub waste and then trying to take this tub out in one piece BUT be prepared to still have a mess from the wall tiles that must be removed prior to removing the tub.