Passing groovy 'lists' via testcase properties...

By the way, below solution given by Smartbear staff also works.

Although not as clean as the one I share in other comment but this also works. If I put all the pieces together what is shared in this post, this is what you have to do (Run tested OK - no changes required below. No addition of property at test case level).

1. Create a test case (say with name TestCase1).
2. Add a groovy script step (say with name Groovy Script1). Add below code here:

import javax.naming.Context

def list = [1,2,3,"adfadfas"]
context.setProperty("list",list)
log.info "from script 1 " + list

3.Add a second groovy script step (say with name Groovy Script2). Add below code here:

import com.eviware.soapui.support.types.StringToObjectMap
def contextMap = new StringToObjectMap( context )

def list1 = contextMap.list
log.info "from script 2" + list1

4. If you want to add another groovy script step (say with name Groovy Script3). Repeat above code:

import com.eviware.soapui.support.types.StringToObjectMap
def contextMap = new StringToObjectMap( context )

def list1 = contextMap.list
log.info "from script 3" + list1

5. Now add a last groovy script to call the above 3 steps (by running the whole test case). Remember to make this step disabled otherwise while running the test case, this step will again call the test case and you will go in a recurring loop. (So Groovy Script4 (disabled)): add below code. 

import com.eviware.soapui.support.types.StringToObjectMap
def contextMap = new StringToObjectMap( context )

def tCase = testRunner.testCase.testSuite.testCases["TestCase 1"]
tCase.run(contextMap, false)

6. Now if you run this disabled step, you will see that the array/list from groovy script1 was passed in all other steps.

note: You can also do the same by adding this run groovy script in another test case and run from there. 

Hope this helps!

Cheers, Pramod