Is the interstate commerce act a valid example of pure socialism?

The Interstate Commerce act has nothing to do with socialism. Socialism has to do with ownership of the means of production and distribution, which means how the surplus value generated by the means of production is used.

It is an example of government interventionism in a market-based economy. It did not attempt to change the method of ownership and allocation of surplus value in the railroad industry, nor did it attempt to introduce worker self-management.