So smartcards is included in what is called HID-devices or Human Interface Devices. Other examples of these are mouse and keyboard.
HID Devices are by default shared between the client and the virtual desktop and is not subject to the general USB redirection policys.
You can however choose to show HID devices in the redirection menu and that way redirect then specifically, the usecase for that if for example dictation-devices that have multiple functions and some needs to be shared and some redirected.
Do you have a specific problem with smartcards?
// Linjo