Bhopal, India was caused by 30 tons on methyl isocyanate. That is similar to what Tianjin is facing... But, probably not as bad.
I used to make NaCN. I dug out our handling brochure. Peroxide and Hypochlorite CAN be used as neutralizers... But, only in dilute forms. If contacted with concentrated NaCN, they’re both very bad news.
Basically... On a scale this size? I think the best they could do would be to evacuate, and spread some weak caustic soda ash over all the potentially contaminated areas. They must keep the water basic.... Even just a little.
God help them. If not handled properly, this has the potential to be catastrophic.
Material Safety Data Sheets are your friend.