Create a new Multi-Tenant (Partitioned) Managed Metadata Service App and configure Content Type Publishing Hub.

Requires an existing site collection at /microsoft/mdhub that is part of the subscription and uses the publishing site template

Watch out for issues with the $proxy in the Set-SPSiteSubscriptionMetatDataConfig - you may need to pass in it's GUID directly

More details soon at www.harbar.net/articles/sp2010mt1.aspx

PowerShell
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<# Sets up service instance & service app and proxy #>

Get-SPServiceInstance | where{$_.GetType().Name -eq "MetadataWebServiceInstance"} | Start-SPServiceInstance

$pool = Get-SPServiceApplicationPool -Identity 'SharePoint Web Services Default'

$meta = New-SPMetadataServiceApplication -ApplicationPool $pool -Name 'Tenant Managed Metadata' -DatabaseName TenantMetadataDB -DatabaseServer sp2010 -PartitionMode

$proxy = New-SPMetadataServiceApplicationProxy -PartitionMode -ContentTypePushdownEnabled -DefaultKeywordTaxonomy -DefaultSiteCollectionTaxonomy -Name 'Tenant Managed Metadata Proxy' -DefaultProxyGroup -ServiceApplication $meta


<# Configures Metadata Specfic Tenant Config #>

Set-SPSiteSubscriptionMetadataConfig -identity $sub -serviceProxy $proxy -hubUri 'http://sp2010/mircosoft/mdhub'