The following action is added to the Ajax module infostore:

Get files of the user shared to other entities

GET /ajax/infostore?action=shares

Parameters:

session – A session ID previously obtained from the login module.
columns – A comma-separated list of columns to return. Each column is specified by a numeric column identifier. Column identifiers for infoitems are defined in Common object data and Detailed infoitem data.
sort (optional) – The identifier of a column which determines the sort order of the response. If this parameter is specified, then the parameter order must be also specified.
order (optional) – asc if the response entires should be sorted in the ascending order, desc if the response entries should be sorted in the descending order. If this parameter is specified, then the parameter sort must be also specified.

Response: An array with infoitem data. Each array element describes one infoitem and is itself an array. The elements of each array contain the information specified by the corresponding identifiers in the columns parameter.

Further details: http://oxpedia.org/wiki/index.php?title=HTTP_API#Get_shared_infoitems_.28S ince_7.8.0.2C_Preliminary.29