Configure buildscript repositories for all project globally in init.gradle?

I have the following: ~/.gradle/init.gradle

allprojects {
    repositories {
        maven {
            url = 'http://mydomain/nexus/content/groups/public'
        }
    }
    buildscript {
        repositories {
            maven {
                url = 'http://mydomain/nexus/content/groups/public'
            }
        }
    }
}

webapp-parent.gradle

buildscript {
    dependencies {
        classpath group: 'org.gradle.api.plugins', name: 'gradle-tomcat-plugin', version: '0.9.8'
    }
}
  apply plugin: org.gradle.api.plugins.tomcat.TomcatPlugin

build.gradle

apply {
    from 'webapp-parent.gradle'
}

Now, when I run the webapp-parent.gradle, it works:

$ ./gradlew -b webapp-parent.gradle
 Download http://mydomain/nexus/content/groups/public/org/gradle/api/plugins/gradle-tomcat-plugin/0.9.8/gradle-tomcat-plugin-0.9.8.jar
...
BUILD SUCCESSFUL

but when I run the build.gradle file, it fails:

$ ./gradlew
  FAILURE: Build failed with an exception.
  * Where:
Build file '/home/wujek/IdeaWorkspace/gradle-test/build.gradle' line: 1
  * What went wrong:
A problem occurred evaluating root project 'gradle'.
> Could not resolve all dependencies for configuration 'classpath'.
   > Could not find org.gradle.api.plugins:gradle-tomcat-plugin:0.9.8.
     Required by:
         unspecified:unspecified:unspecified

What am I doing wrong?

wujek