The WMTSGetFeatureInfo control allows retrieval of information about features displayed in a WMTS layer.
This example uses an OpenLayers.Control.WMTSGetFeatureInfo control layer to access information from WMTS layers. The control is activated and configured to request feature information when you click on the map. If the control's drillDown property is set to true, multiple layers can be queried.
See the wmts-getfeatureinfo.js source to see how this is done.