According to this article, no.  But I disagree.

I agree that employee advocates are not the same as influencers.  

Employees have a role to play when it comes to social media amplification of content but when advocacy programs are optimised correctly, you will encourage employees to have a healthy mix of content that speaks to their interests first rather than brand interests first.

Using employees as megaphones and social sharers for brand content (as suggested in this article) isn't a best practice I would recommend.

However, some employees in your organisation will be subject matter experts.  

They are the people who have a natural passion and curiosity for learning.  They're credible with customers. 

These are your lawyers and your pre-sales consultants - not necessarily your leaders and executives!

They become influential not because they're product experts but because they understand their industry.

Now these employees do have the ability to become influencers in their own right - even though they work for your company.

I've worked alongside several people who have built credible, independent influence whilst being employed including Timo Elliot, Oliver Bussman, Marcell Vollmer and others.

Can this conflict with the interests of their employer?

Sure, sometimes it can but when you focus your experts to talk beyond conversations about product, this conflict can be avoided.

Opinions about issues, market trends and thought leadership is where most employed influencers can build their messaging.

Do employee influencers replace external influencers?

Absolutely not.  However, the relationship with external influencers may change slightly.  

Rather than transactional contracts between brand and influencer (for paid promotional work) we may see more longer-term relationship led approaches where external influencers are aligned to employee influencers to co-create content.

So, whilst I agree advocacy doesn't equate to influence I do believe that some employees in your organisation can become influencers in their own right with the right guidance and support along the way.