Any moving assistance is treated like a taxable bonus for any other reason. The total amount is subject to income tax and must be included in your W-2 wages. For example, if the employer intended to give you $5000 of moving assistance and they actually paid $8000 to cover the taxes as well, then the total amount of $8000 must be included in your W-2 wages.
You simply report your actual wage income, regardless of how you spent it. Then, I believe moving expenses are still listed on the deductions and credits page in the section for job-related expenses. You can list the actual moving expenses that you paid that you can prove with receipts, regardless of how much assistance you actually received. Although it is not a federal deduction, it is still entered on the main federal page, and it will flow to your state tax return automatically if it is an allowable deduction in your state and if you meet any other state requirements.
