Not a tax attorney or anything but I work in financial services in a field that is heavily impact by mobility taxation and the like (tax withholding for employees who work/live in multiple tax jurisdictions).
A players residence, at least with regard to NY taxes, would have no bearing on the tax due to NY. They are employed in NY, and would have to pay NY tax on the income. A signing bonus would be considered taxable income the same as salary, I am fairly certain there is no distinction from a tax point of view. There may be some factors involved that could potentially reduce the tax liability since the player isn't employed for all 12 months, technically, which could save them from potentially being taxed for the offseason (ie, they have to pay 9/12ths of the NY tax rate since they only work a portion of the year in NY) although I suspect even that would be a tough sell for an accountant since they are a contract employee who is paid their entire salary for ~9 months work.
Also as someone else pointed out, there's a good chance the signing bonus is still subject to jock tax in other jurisdictions as way. I wouldn't bet money on this but its certainly a possibility.