I suppose, to start the conversation, and also to act as a bump:
There's no doubt that the political relationship between socialist and capitalist powers would still be a highly negative one. Market Socialism still detests the bourgeoisie just as any another Socialist strain, and the rhetoric is the same. In the economic relationship, we may see greater variation between countries. If, say, the USSR were market Socialist, they probably would seek to limit economic activity with capitalists. However, how the workers would react that would be negative. If they were working in co-ops, then the government would be cutting off a large market. That ties back to how market Socialism would affect governments, if it would be less authoritarian than OTL Marxist-Leninism. Lesser market Socialist countries I can see developing a positive economic relationship with capitalists, like OTL China except it follows a different Socialist strain.