In comic books, an intercompany crossover is a comic or series of comics where characters that at the time of publication are the property of one company meet those owned by another company.

解析：以上有3个谓语动词，则有2个连词引导从句，关系副词where引导定语从句，关系代词that引导定语从句,that引导定语从句是修饰/限定where定语从句种的主语character.

句子语法结构分析如下

状语：In comic books

主语：an intercompany crossover

系动词：is

表语：a comic or series of comics 

修饰表语定语从句：where characters that at the time of publication are the property of one company meet those owned by another company.

修饰表语定语从句语法结构分析如下

引导定语从句关系副词:where

主语：characters

修饰主语定语从句：that are the property of one company at the time of publication

谓语：meet

宾语：those

修饰宾语定语：owned by another company