Azure – Getting Output Values from Linked ARM Template

hoping someone can help pinpoint what's missing in my approach.

I'm using visual studio 2017 if this makes any difference.

I've two arm templates; maintemplate and the linkedtemplate.

In the maintemplate I'm trying to reference a linked template and retrieve an output value from it in my maintemplate's outputs section so that the outputs contains values from both the templates.

Here is the linkedtempalte outputs section;

"outputs": {
    "LoadBalancer-pip1": {
      "type": "string",
      "value": "[reference(resourceId('Microsoft.Network/publicIPAddresses',variables('publicIPAddressName1'))).IpAddress]"
    },
    "LoadBalancer-pip1-DNS-Name": {
      "type": "string",
      "value": "[reference(resourceId('Microsoft.Network/publicIPAddresses',variables('publicIPAddressName1'))).dnsSettings.fqdn]"
    }
  }

Here is the maintemplate outputs section;

"outputs": {
    "jump Box VM Public IP address": {
      "type": "string",
      "value": "[reference(resourceId('Microsoft.Network/publicIPAddresses',variables('hub-cc-jbox-pipName'))).IpAddress]"
    },
    "Load Balancer VIP1": {
      "type": "string",
      "value": "[reference('hub-plb').outputs.LoadBalancer-pip1.value]"
    },
    "Load Balancer VIP1 DNS Name": {
      "type": "string",
      "value": "[reference('hub-plb').outputs.LoadBalancer-pip1-DNS-Name.value]"
    }
}

Accordingly to this link; https://docs.microsoft.com/en-us/azure/azure-resource-manager/resource-group-linked-templates#link-or-nest-a-template

it should be possible as long as it's not a nested template, which it's not.

Here is my maintemplate section where I'm making the link to the linkedtempalte;

{
        "name": "hub-plb",
        "type": "Microsoft.Resources/deployments",
        "apiVersion": "2017-05-10",
        "dependsOn": [],
        "properties": {
          "mode": "Incremental",
          "templateLink": {
            "uri": "[concat(parameters('_artifactsLocation'), '/', variables('hub-plbTemplateFolder'), '/', variables('hub-plbTemplateFileName'), parameters('_artifactsLocationSasToken'))]",
            "contentVersion": "1.0.0.0"
          },
          "parametersLink": {
            "uri": "[concat(parameters('_artifactsLocation'), '/', variables('hub-plbTemplateFolder'), '/', variables('hub-plbTemplateParametersFileName'), parameters('_artifactsLocationSasToken'))]",
            "contentVersion": "1.0.0.0"
          }
        }
      }

When I try to validate / deploy the template it fails with this message;

VERBOSE: Performing the operation "Creating Deployment" on target "xyz-rg".
08:23:09 - New-AzureRmResourceGroupDeployment : 8:23:08 AM - Error: Code=InvalidTemplate; Message=Deployment template validation 
08:23:09 - failed: 'The template output 'Load Balancer VIP1' at line '1034' and column '31' is not valid: The language expression 
08:23:09 - 'reference('hub-plb').outputs.LoadBalancer-pip1.value' is not valid: the string character 'p' at position '42' is not 
08:23:09 - expected..

Any help much appreciated.