Is virtual network peering across azure tenants possible?

I'm trying to use the new Azure Virtual Network public preview of the peering feature to join two networks I have on two different subscriptions, i.e. different tenants. Is this possible, I've not seen anything to say otherwise, but when I try to peer them in PowerShell I get the following error.

The client has permission to perform action 'Microsoft.Network/virtualNetworks/peer/action' on scope '/subscriptions/{Guid2}/resourceGroups/Default-Sydney/providers /Microsoft.Network/virtualNetworks/SYDVN/virtualNetworkPeerings/LinkToSYDVN', however the linked subscription '{Guid1}' is not in current tenant '{Guid3}'.

Full error and command

PS C:\Windows\system32> Add-AzureRmVirtualNetworkPeering -name LinkToSYDVN -VirtualNetwork $SYDVN -RemoteVirtualNetworkId "/subscriptions/{Guid1}/resourceGroups/Default-Sydney/providers/Microsoft.Network/virtualNetworks/SYDVN1" -BlockVirtualNetworkAccess
WARNING: The output object type of this cmdlet will be modified in a future release.
Add-AzureRmVirtualNetworkPeering : The client has permission to perform action 'Microsoft.Network/virtualNetworks/peer/action' on scope '/s
ubscriptions/{Guid2}/resourceGroups/Default-Sydney/providers/Microsoft.Network/virtualNetworks/SYDVN/virtualNe
tworkPeerings/LinkToSYDVN', however the linked subscription '{Guid1}' is not in current tenant
'{Guid3}'.
StatusCode: 403
ReasonPhrase: Forbidden
OperationID : '{Guid4}'
At line:1 char:1+ Add-AzureRmVirtualNetworkPeering -name LinkToSYDVN -VirtualNetwork $S ...+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+ CategoryInfo          : CloseError: (:) [Add-AzureRmVirtualNetworkPeering], NetworkCloudException+ FullyQualifiedErrorId : Microsoft.Azure.Commands.Network.AddAzureVirtualNetworkPeeringCommand

Any help will be much appreciated.