It is, if there antenna leads in the system for a WWAN card.   If there are not, retrofitting them is just about impossible -- if there are no antenna leads and you need WWAN support, use a USB WWAN adapter.  
Hi,   I recently purchased a Dell Latitude 5490 and I noticed it is the model without the Smartcard reader and Cellular option. I opened the bottom panel to install a WLAN card for WiFi and noticed that there is a slot for a WWAN card, so this had me wondering if I could purchase a WWAN card and install it, then put a SIM card into the slot. I did notice that the SIM card tray is capped off as it is not a feature used in this model, but it can be removed, so I could purchase a SIM card tray and install the SIM as the SIM card reader is built into the computer. Let me know if this is technically possible.   Kind regards, Lewis Brumby
Dell Latitude 5490 Cellular Query