Since the link is created dynamically (using jquery), and then the HTML of that object is consumed, the handler will not be part of the HTML. So in this case, the link has to be created out of string directly:
formatter: function(cellvalue, options, row) {
var handler = "someHandlerDefined(" + options.rowId + ")";
return "<a href=# onclick='" + handler + "'>Link</a>";
}
That worked!