There's a decent argument I heard in a book called How Capitalism Ends that makes a solid argument for the recognition of the Technocracy (and kind of the PMCs for similar reasons) as a separate class from both the bourgeoisie and the proletariat in recent times, here's the excerpt:

It’s important to note that the technocracy are not excluded from the proletariat because they earn too much money, or because they enjoy a large degree of autonomy in their work. It is the effective (though incomplete) control they exercise over productive assets by virtue of their technical knowledge that separates them from the proletariat. They make largely autonomous decisions about how and where productive assets will be deployed, and the expert knowledge which gives them the ability to do so puts them in a different relationship to both the means of production and to the bourgeoisie than that of the proletarian. At the same time, they do not enjoy the full range of ownership rights over the assets they control – they cannot sell or bequeath them for example. This limitation sets them apart from the petty-bourgeoisie.

Most of these traits are shared by the PMC as well

The book's decent but it's fairly anti AES (although it only comes up like twice in the whole book and for less than a couple sentences each time) and a little bit trot so tread carefully. Very good for getting new lefties on board with the economics of Marxism without having to have them buy into China good immediately.