Dawn, is your question cutting the angle or cutting thru the ties. With 135 degrees, this should be easy since it is a reciprocal of 45 degrees, meaning that they total 180 degrees, or a straight line.
If the question is cutting through the tie, then you should be able to cut through from top and bottom with a power circular saw. They also make a power reciprocating saw, like a big saber saw that is often used in demolition work, that should be able to cut through any remaining thickness. Or if you only have to make one cut or so and you don't need it to be carpenter quality, you can get a bow saw for about $10 at any home center. This should be nicely able to complete circular saw cuts. These have coarse teeth and are hard to keep on a line, but they will make or finish a cut. These are usually used for tree trimming work. A chain saw would also work, of course, and an electric one can be had for under $50. When using any power tools, be sure to read, understand and follow the instructions that come with the tool. (Wonder where I heard that?) And if you rent any of these, or other tools, be sure to ask for the safety instructions from the rental agency.
If this hasn't answered your question, let us know more about your problem.