A Google Groups thread asks if one can transfer their Google Advertising Professional exam scores from their old company to their new company. The Google Advertising Professional program was launched in 2004 to help Google give certification to professionals selling AdWords services. Part of the certification is completing an exam to earn rights to show the Google Advertising Professional Certification Logo on your site.

So when employees move from company to company, they may bring along their individual certification status. But if the company has not received the certification on the company level, it seems like when an employee with the certification leaves, it goes with the individual.

But in cases where the company earned the certification, it cannot be transferred from an old company to a new one.

According to AdWordsPro.Jordan, an official Google AdWords representation, in a Google Groups thread, you cannot transfer the certification:

Forum discussion at Google Groups.