It is possible to login with your GW1 account on the GW2 website, without having a copy of GW2 linked to it, and see the following message:
Your Guild Wars accounts are linked
Congratulations! You have successfully linked your Guild Wars and Guild Wars 2 accounts. In doing so, you now have access to the exciting rewards awaiting you inside the Hall of Monuments. The following Guild Wars 2 account information will now be used to log in to both Guild Wars and Guild Wars 2:
Account Name: example@e-mail.com
Which is incorrect.