Dual agency mischief in commercial real estate?

[Tyrrell Levine]

Hi all, I'm trying to understand how the big commercial real estate agents (CBRE, JLL, etc) market deals. For example, if I want to sell a five-unit multifamily in Washington DC, it seems these agencies will market almost exclusively to their own clients -- and thus end up on both sides of the deal (dual agency). 

Is this how it actually works? If so, it seems like they are not marketing to the vast majority of potential buyers (because even these big players have <20% market share in any given market). And thus how are they achieving the highest possible selling price?

I'm also wondering if working with a smaller listing agent might be a way to avoid this dual agency problem. Any insights from the BP community would be greatly appreciated.