And using the URL above, the LayerID looks to be similar. I too was expecting something like "Contract Boundary_6637", but this seems to be what it is.
{ "id": "http://image.durham.ca/ArcGIS/rest/services/Works/Land/MapServer", "layerType": "ArcGISMapServiceLayer", "url": "http://image.durham.ca/ArcGIS/rest/services/Works/Land/MapServer", "visibility": false, "visibleLayers": [ ], "opacity": 1, "title": "Land (Easements, Contract Boundaries)", "layers": [ { "id": 0, "popupInfo": { "title": "Easement", "fieldInfos": [ { "fieldName": "OBJECTID", "label": "OBJECTID", "tooltip": "", "visible": false, "stringFieldOption": "textbox" }, { "fieldName": "INST_NO_S", "label": "INST_NO_S", "tooltip": "", "visible": false, "stringFieldOption": "textbox" }, { "fieldName": "INST_NO_W", "label": "INST_NO_W", "tooltip": "", "visible": false, "stringFieldOption": "textbox" }, { "fieldName": "PLAN", "label": "PLAN", "tooltip": "", "visible": false, "stringFieldOption": "textbox" }, { "fieldName": "CATERGORY", "label": "Category:", "tooltip": "", "visible": true, "stringFieldOption": "textbox" }, { "fieldName": "RE_CODE", "label": "RE_CODE", "tooltip": "", "visible": false, "stringFieldOption": "textbox" }, { "fieldName": "TYPE", "label": "Type:", "tooltip": "", "visible": true, "stringFieldOption": "textbox" }, { "fieldName": "TYPE2", "label": "TYPE2", "tooltip": "", "visible": false, "stringFieldOption": "textbox" }, { "fieldName": "MUNICIPALITY", "label": "Municipality", "tooltip": "", "visible": false, "stringFieldOption": "textbox" }, { "fieldName": "SEWER", "label": "Sewer:", "tooltip": "", "visible": true, "stringFieldOption": "textbox" }, { "fieldName": "WATER", "label": "Water:", "tooltip": "", "visible": true, "stringFieldOption": "textbox" }, { "fieldName": "SHAPE", "label": "SHAPE", "tooltip": "", "visible": false, "stringFieldOption": "textbox" }, { "fieldName": "SHAPE.AREA", "label": "SHAPE.AREA", "tooltip": "", "visible": false, "format": { "places": 2, "digitSeparator": true }, "stringFieldOption": "textbox" }, { "fieldName": "SHAPE.LEN", "label": "SHAPE.LEN", "tooltip": "", "visible": false, "format": { "places": 2, "digitSeparator": true }, "stringFieldOption": "textbox" } ], "description": null, "showAttachments": true, "mediaInfos": [ ] } }, { "id": 1, "popupInfo": { "title": "Contract Boundary", "fieldInfos": [ { "fieldName": "OBJECTID", "label": "OBJECTID", "tooltip": "", "visible": false, "stringFieldOption": "textbox" }, { "fieldName": "CONTRACTNO", "label": "Contract Number:", "tooltip": "", "visible": true, "stringFieldOption": "textbox" }, { "fieldName": "CONTRACTSTATUS", "label": "Contract Status:", "tooltip": "", "visible": true, "stringFieldOption": "textbox" }, { "fieldName": "SHAPE", "label": "Shape", "tooltip": "", "visible": false, "stringFieldOption": "textbox" }, { "fieldName": "SUB_PER", "label": "Substantial Performance:", "isEditable": false, "visible": true, "stringFieldOption": "textbox" }, { "fieldName": "FINAL_ACCEP", "label": "Final Acceptance:", "isEditable": false, "visible": true, "stringFieldOption": "textbox" }, { "fieldName": "SWAT", "label": "SWAT:", "isEditable": false, "visible": true, "stringFieldOption": "textbox" }, { "fieldName": "SHAPE_Area", "label": "SHAPE_Area", "isEditable": false, "visible": false, "format": { "places": 2, "digitSeparator": true } }, { "fieldName": "SHAPE_STArea__", "label": "SHAPE.STArea()", "isEditable": false, "visible": false, "format": { "places": 2, "digitSeparator": true } }, { "fieldName": "SHAPE_STLength__", "label": "SHAPE.STLength()", "isEditable": false, "visible": false, "format": { "places": 2, "digitSeparator": true } }, { "fieldName": "SHAPE_Length", "label": "SHAPE_Length", "isEditable": false, "visible": false, "format": { "places": 2, "digitSeparator": true } } ], "description": null, "showAttachments": true, "mediaInfos": [ ] } }, { "id": 2, "popupInfo": { "title": "Depot Area: {DEPOTAREA}", "fieldInfos": [ { "fieldName": "OBJECTID", "label": "OBJECTID", "tooltip": "", "visible": false, "stringFieldOption": "textbox" }, { "fieldName": "SHAPE", "label": "SHAPE", "tooltip": "", "visible": false, "stringFieldOption": "textbox" }, { "fieldName": "DEPOTAREA", "label": "DEPOTAREA", "isEditable": false, "visible": false, "stringFieldOption": "textbox" }, { "fieldName": "SHAPE_STArea__", "label": "SHAPE.STArea()", "isEditable": false, "visible": false, "format": { "places": 2, "digitSeparator": true } }, { "fieldName": "SHAPE_STLength__", "label": "SHAPE.STLength()", "isEditable": false, "visible": false, "format": { "places": 2, "digitSeparator": true } }, { "fieldName": "SHAPE_Length", "label": "SHAPE_Length", "isEditable": false, "visible": false, "format": { "places": 2, "digitSeparator": true } }, { "fieldName": "SHAPE_Area", "label": "SHAPE_Area", "isEditable": false, "visible": false, "format": { "places": 2, "digitSeparator": true } } ], "description": null, "showAttachments": true, "mediaInfos": [ ] } } ] },