1）如果整句话是陈述发生在2012年这个时间点的现实情况,用简单过去式表达即可；如果意思是 “截至2012年,已有23个.” 那么才有必要考虑完成时.不过介词就需改一下：By 2012,...
2）句子以简洁易懂为优,lay 和 establish 意思相近从句写得复杂了一点.
3) comprehensive financial report 当中不宜插入 government,因为这个词组对其他公民营企业也适用,government 可以前置加所有格,甚至省略.
试改写两种：
By 2012,23 provinces in the country have already compiled their trial version of the governments' comprehensive financial reports,which has established a solid foundation for a formal financial reporting system.
In 2012,23 provinces in the country compiled their trial version of the governments' comprehensive financial reports,establishing a solid foundation for a formal financial reporting system.