You still seem to be expecting a nice human readable string when what you are being passed is a binary data structure. The docs for the COM server say it returns an ArrayList (a .Net/C# data type of some sort) but this has to be translated to something that can be sent through the COM interface, which must remain language agnostic. The QAxBase docs imply this structure is a SAFEARRAY(BYTE). I'd hazard a guess it's a single dimensional array of VT_VARIANT entries.

In your C++ Qt application you receive a QByteArray. Use QByteArray::toHex() to dump the first 24 or 32 bytes. Then sit and try to marry the bytes to the SAFEARRAY structures described here;
http://msdn.microsoft.com/en-us/library/aa913233.aspx
Qt Code: 
  1. typedef struct FARSTRUCT tagSAFEARRAY {
  2.   unsigned short cDims;   // two bytes
  3.   unsigned short fFeatures;  // two bytes
  4.   unsigned short cbElements;  //two bytes
  5.   unsigned short cLocks;  // two bytes
  6.   unsigned long handle;  // four bytes
  7.   void HUGEP* pvData;  // four bytes
  8.   SAFEARRAYBOUND rgsabound[1];  // structure below repeated if more than one dimension in array
  9. } SAFEARRAY;
  10.  
  11. typedef struct tagSAFEARRAYBOUND {
  12.   unsigned long cElements; // four bytes
  13.   long lLbound;  // four bytes
  14. } SAFEARRAYBOUND;
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Does the number of dimensions make sense? Do the array bounds make sense? If so, read here:
http://msdn.microsoft.com/en-us/library/ms221145.aspx
You might want to use your favourite search engine to look for a C++ wrapper for SAFEARRAYs.