Note that this may not be covering answers to your questions, rather posting what I noticed.
com.eviware.soapui.junit - package is not there in following files. This might be the reason for getting the error.
1. soapui-pro-4.5.1.jar
2. soapui-4.5.1.jar
3. soapui-pro-SNAPSHOT.jar (this is from maven repo you mentioned, may be it is not renamed to 4.5.2 on the maven repo, a guess)
Got a 4.5.1 version. Noticed below and hoping it would be same 4.5.2 as well.
Not sure if it is noticed, soapui-pro-4.5.1.jar file (of same size) is available under $SOAPUI_HOME/bin, $SOAPUI_HOME/lib directories.
And soapui-4.5.1.jar of $SOAPUI_HOME/lib is huge file than other file.
May be the class you were looking for might be available in $SOAPUI_HOME/lib/soapui-4.5.2.jar.
