A spokesperson for the Barbican assures me that it's a hall hire and nothing to do with their own in-house artistic planning.
She says: "This concert is a rental of the Barbican Hall with the marketing of the event undertaken by an outside promoter, and while the concert does fall on International Women’s Day it was not programmed to mark this event. The Barbican had not been sent or approved this version of the advert and had not been made aware that the promoter intended to market it in this way. We recognise that it is entirely inappropriate to claim any link between the concert and International Women’s Day and have instructed the concert promoter to remove all mention of this from any future advertising copy.
"Having spoken to the promoter since this advert was brought to our attention, it appears that the promoter and orchestra had misunderstood the focus of International Women’s Day on celebrating the social, economic, cultural and political achievement of women. They informed us that they included the mention in the advert as the focus and ways of celebrating International Women’s Day are different in former Soviet Union countries. This in no way excuses the advert making this link, I just wanted to give you some context to try to explain how this error has occurred!
"...We absolutely agree that it was entirely inappropriate for the promoter to make this link between the concert and International Women’s Day the way it is understood in the UK/more internationally."
Apparently in Russia International Women's Day is a bit like Valentine's Day, with flowers and pretty stuff, etc. - so a celebration of traditional femininity rather than of women's achievements. Very different from London.
Photo from Alechetron.com