Yes. It is possible to use Web Map Tile Service (WMTS) layers in ArcGIS Collector. The WMTS layer must be added as a layer in a web map or used as a basemap in ArcGIS Online. To do so, refer to the instructions provided in ArcGIS Online: OGC WMTS web service.
The image below shows a WMTS layer from the OS Data Hub API added to a web map in ArcGIS Online.
The image below shows a WMTS layer loaded using the OS Data Hub API in ArcGIS Collector.