In the following you will see that Erlang C was used for data traffic, the key factor being delay rather than blocking.
If you use the same concepts of Erlang C, but redefine the erlang to mean the amount of bits it takes to keep a traffic sensitive facility busy for 1 second, you can easily figure it out. Unfortunately, there are no Erlang C tables included so you will need to find some to figure it out.
http://www.cisco.com/univercd/cc/td/doc/cisintwk/intsolns/voipsol/ta_isd.pdf