It's a £75 million project being set up and run by a charity, the Garden Bridge Trust, so it won't be publicly owned. It will be closed to the public when it's rented out for commercial purposes.
The FAQ says:
Over 65% of the capital costs to build the bridge will be fundraised from the private sector. More than £145 million has been pledged already and there is a business plan to cover the £2 million annual maintenance and operations costs. Transport for London and the Government have together contributed £60 million in total.
The arguments for the public funding contribution are that commuters will be able to walk across it, and it will help regenerate the areas at both ends.
The FAQ says:
Over 65% of the capital costs to build the bridge will be fundraised from the private sector. More than £145 million has been pledged already and there is a business plan to cover the £2 million annual maintenance and operations costs. Transport for London and the Government have together contributed £60 million in total.
https://www.gardenbridge.london/questions-answers/fact-ficti...
The arguments for the public funding contribution are that commuters will be able to walk across it, and it will help regenerate the areas at both ends.