In short, "Dynamic MDX Queries" don’t work as described in the BOL.
I’ve lifted the sample code directly, tried to run it, and it fails.
It’s documented at http://msdn.microsoft.com/en-us/library/ms172589(SQL.90).aspx

The “Analysis Services Event Provider” queries a SQL table, generates
XML output, passes it through an XSLT style sheet, and generates an
MDX query dynamically. Using the documented example, no MDX is created
as seen in the event log error below: (The “MDX Query String” is
blank).

Event Type:       Error
Event Source:    NotificationServices
Event Category: None
Event ID:           2976
Date:                3/26/2009
Time:                6:59:10 PM
User:                N/A
Computer:         MyServer
Description:
Description: The AnalysisServicesProvider event provider failed while
running an MDX query. The provider will be terminated.
EventParameters:
 Provider Name: TerminalEventNsEventProvider
 MDX Query String:

Description: ExecuteReader: CommandText property has not been
initialized
InstanceName: IodNS
ApplicationName: DashboardNotifications
Component: Event collection
Thread: 10

I’ve tried countless variations and “pass-through” XSLT and I can’t
get anything past this point.

Can someone at MS redirect to the SSNS support group?