Contactless detection of current
Your question is a bit ambiguous, but the answer to the "general" question, is yes.  It is possible to sense the current in a single wire inside (surrounded by) other wires. The only requirement is that the current being used, must pass through only one wire (at a time).
To clarify...
You place a current sensor around all wires. Run a current through one of the wires.  You should be able to sense the current with no problem.  

On the other hand, if you mean detect (differentiate) one particular current when other "close by" wires are also carrying different currents, it may be extremely hard.