WWAN 5540 and Latitude E6520

Have you tried installing the drivers for the 5550 card they are available on the drivers and download page. If the two cards are similar the drivers may work. e.g. I installed the Dell 355 bluetooth module using a Dell bluetooth 370 driver for windows 7. 

Driver: R298998

Application: R298995

Regarding Latitude E6420/6520 and Dell 5540 Mobile wireless. I've tried every driver listed on Dells website and none will install this device in these machines. Possibly because they are new. Note I said none will install because Dell has rigged the installer to compare the machine type to a list of approved machines and when it sees it is trying to install the driver into one of the above laptops, it stops the installation. The card will work if you can figure out how to install the driver. The driver install routine can be hacked to bypass the test but it's an ordeal unless you are a programmer. Not worth it. I became totally frustrated and returned the device to Dell. Others more patient than I have managed to install the driver so the laptop would recognize and work with that device. Life is too short and Dell is way too shortsighted. I am still trying to identify and purchase a radio mini-card that will work in this machine. In the meantime I have left it home for two trips and taken my trusty old T61p with a radio card that works.  Should have ordered it (the WAN card)  with the machine but was not intending to use it that way. Dell's support in this regard has been way under par. I'vs spent hours holding and suffered a dozen disconnects. Customers not treated this way by Dell's competion. I'm about convinced to go back to previous vendor personally and insist my company do the same.

How do you rip the drivers as you have done?

you can use winrar or universal extractor (free programs)