You can use NI Measurement Studio (and therefore .NET languages such as C#, VB) to work with shared variables via NI's suite of assemblies.
Other than that, not directly via PSP. As to why, that's probably due to the proprietary nature and general lack of visibility of LabVIEW / G.
Note that the NI Shared Variable Engine also exposes Network-Published Shared Variables over OPC DA. So any OPC DA client can access the variables. A number of programming languages have libraries that support connecting to OPC DA servers.
