During an inquest into the death earlier this year the Oxleas NHS Foundation Trust, which oversees Green Parks House, said Mrs Mager's death "could not have been predicted or prevented".
But after court proceedings were served, the Trust admitted liability, saying they should have prevented her death.
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The painting, entitled 'Beautiful Beautiful George Michael Love Painting', was auctioned to help raise funds for HIV and Aids prevention.
The 38-year-old victim was standing on a busy Victoria Line train when another passenger approached him.