Azure Bicep跨订阅引用现有资源（三元运算符）报错求助

在Azure Bicep文件中尝试根据输入参数，引用不同订阅、资源组中的现有Application Insights资源时，设置scope属性触发如下错误：

The resource namespace 'subscriptions' is invalid. (Code: InvalidResourceNamespace)

当前使用的相关代码：

param prefix string = ''
@allowed([
  'dev'
  'test'
  'prod'
])
@description('Deployment environment type.')
param deploymentEnvironment string

var isProd = deploymentEnvironment == 'prod'
var isTest = deploymentEnvironment == 'dev'
var usingExistingAin = prefix == 'mrax' && (isProd || isTest)
var prodOrTestlabNameTest = isProd ? 'appInsightsName1' : 'appInsightsName2'
var subscriptionIdTest = usingExistingAin ? (isProd && usingExistingAin ? 'subscriptionID1' : 'subscriptionID2') : subscription().id


resource applicationInsightsResource 'Microsoft.Insights/components@2020-02-02' existing = {
    name: usingExistingAin ? prodOrTestlabNameTest : appInsightsName 
    scope: resourceGroup(subscriptionIdTest, rsgNameTest)
}

注：isTest的条件设置是正确的

另外，由于权限限制，无法采用定义两个资源分支的方式（如下示例代码会触发授权错误），因此需要其他解决办法：

AuthorizationFailed","message":"The client 'clientId' with object id 'objectId' does not have authorization to perform action 'Microsoft.Insights/components/read' over scope '/subscriptions/subID/resourcegroups/resourceGroupName/providers/Microsoft.Insights/components/appInsightsName' or the scope is invalid. If access was recently granted, please refresh your credentials."

分支方式的示例代码：

param storageAccountName string
param location string = resourceGroup().location

@allowed([
  'new'
  'existing'
])
param newOrExisting string = 'new'

resource saNew 'Microsoft.Storage/storageAccounts@2023-04-01' = if (newOrExisting == 'new') {
  name: storageAccountName
  location: location
  sku: {
    name: 'Standard_LRS'
  }
  kind: 'StorageV2'
}

resource saExisting 'Microsoft.Storage/storageAccounts@2023-04-01' existing = if (newOrExisting == 'existing') {
  name: storageAccountName
}

output storageAccountId string = ((newOrExisting == 'new') ? saNew.id : saExisting.id)

内容的提问来源于stack exchange，提问作者kopolomo