According to the Accessible Rio website:
“About 10 years ago an extensive renovation was carried out, which installed elevators, accessible toilets and escalators to reach the feet of the statue, making it very accessible. Don’t be afraid of the escalators, because trained employees will assist you. If you use a power wheelchair, you may have to transfer to a manual chair (provided by the administration), climb the escalators, and then transfer back to your wheelchair.”
You can read more here: http://accessiblerio.com/en/home/wheelchair-accessible-things-to-do-in-rio/wheelchair-accessible-tourist-attractions-in-rio/christ-the-redeemer/