Running UIAutomation scripts from Xcode

Did anyone succeed in setting up automated UIAutomation tests in Xcode?

I'm trying to set up a target in my Xcode project that should run all the UIAutomation scripts I prepared. Currently, the only Build Phase of this target is this Run Script block:

TEMPLATE="/Applications/Xcode.app/Contents/Applications/Instruments.app/Contents/PlugIns/AutomationInstrument.bundle/Contents/Resources/Automation.tracetemplate"
MY_APP="/Users/Me/Library/Application Support/iPhone Simulator/6.0/Applications/564ED15A-A435-422B-82C4-5AE7DBBC27DD/MyApp.app"
RESULTS="/Users/Me/Projects/MyApp/Tests/UI/Traces/Automation.trace"
SCRIPT="/Users/Me/Projects/MyApp/Tests/UI/SomeTest.js"
instruments -t $TEMPLATE $MY_APP -e UIASCRIPT $SCRIPT -e UIARESULTSPATH $RESULTS

When I build this target it succeeds after a few seconds, but the script didn't actually run. In the build log I get these errors:

instruments[7222:707] Failed to load Mobile Device Locator plugin
instruments[7222:707] Failed to load Simulator Local Device Locator plugin
instruments[7222:707] Automation Instrument ran into an exception while trying to run the script.  UIATargetHasGoneAWOLException
+0000 Fail: An error occurred while trying to run the script.
Instruments Trace Complete (Duration : 1.077379s; Output : /Users/Me/Projects/MyApp/Tests/UI/Traces/Automation.trace)

I am pretty sure, that my javascript and my run script are both correct, because if I run the exact same instruments command in bash it works as expected. Could this be a bug in Xcode?