By random projections, do you mean random connections forming between hubs , or a more directed formation of projections, like the association/dissociation of neuronal assemblies (Gerstein, G. L., Bedenbaugh, P., and Aertsen, M. H. 1989. Neuronal assemblies. IEEE Trans. Biomed. Eng. 36, 4–14) - ?
Ed Bullmore wrote a fascinating paper using graph theory to describe this phenomenon (“Small World Brain Networks”, Basset , A. and Bullmore, E., Neuroscientist, 12, 6, 2006).
IMHO, random connection and pruning processes came earlier in evolutionary history, the process becoming more directed with the emergence of more complex and hierarchical brains, directed by the goal of increasing fitness for the organism.