no you can't:

[ERROR] /home/aaron/src/kiji/kiji-schema-shell/src/main/scala/org/kiji/schema/shell/ddl/AlterLocalityGroupPropertyCommand.scala:51: error: type mismatch;
[INFO]  found   : scala.collection.mutable.Buffer[org.kiji.schema.avro.LocalityGroupDesc]
[INFO]  required: Seq[java.util.List[org.kiji.schema.avro.LocalityGroupDesc]]
[INFO]     layout.setLocalityGroups(newGroups: _*)