The short answer to this question is "no".
Let's take Ethernet as an example. The 10Mbps is the actual bandwidth of the cable. 40% average utilization of an Ethernet network would be considered high. At times a single node may use up to 60% of the available bandwidth but this is uncommon.
Then there are hardware and software issues. How efficient are the hardware and software? Is the data being read from disk or RAM?
There is no way to say how fast a given computer will be at doing network transfers unless you actually test it. There is no test data for Apple's Macintosh systems.╩
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