Either the subsidies take into account the carbon tax or they don't. If they do then it's number rearranging. Government gives dollars and then immediately takes some of them back, it's a convoluted appropriations bill. If they don't then food prices go up which is contrary to the government's goal of keeping food cheap at the point of sale.
If you want to reward reducing carbon emissions by giving additional dollars or paying for more expensive but better for the environment equipment then that could potentially be effective.