No.
A wheelchair which is going to be used in a wheelchair accessible vehicle must be approved for transport in a WAV after being crash tested.
If a wheelchair has been certified for use within a vehicle it will be marked on the wheelchair. The wheelchair will display an anchor symbol (below) on the frame of the wheelchair, usually on the front of the wheelchair frame.
Wheelchairs that have not been tested should not be used in a vehicle and may not be able to be secured safely.
It is your responsibility to make the sure the wheelchair is safe and fitted securely.