you can bind an email to your xbox account to be able to play it on a PC -
the difference to ‘transferring’ a xbox account is that it will still be a xbox account instead of a ‘fully fledged’ pc account so you cannot use the market place and Gaijin store etc but still have to use the microsoft / xbox store (and have to unlock purchases on the xbox) and if you buy a vehicle pack on the xbox that is coming with premium account time the (additional) premium time will not be available on the PC (the vehicle itself will be available though)
however with the recent changes to ‘running the game from Steam’ this won’t work as you don’t get a login screen (where you can enter you xbox account details) by default so you either have to use the standalone client, use the ‘launch manual game update’ option on Steam, run the WT launcher in the game folder manually or edit a settings file…
most easy way would be to bind an email to your xbox account (follow the instructions) and use the WT standalone client imho