jm R½ÕÈØÎÊ!Jrñ´U?´`aÄ&OÓñL©There won't be a fork. BU with long chains is compatible with ABC or any other node. To long to explain here but there is in BU a way to handle the double spend vectors.
https://whatsonchain.com/tx/6df922e69589072ab8793b0523217dd671cea3201c3f1d7f17a7614bca700c31