CiviCRM Entity Tags does not appear in Rules
Try this:

{ "rules_self_create_user_account_and_login" : {
"LABEL" : "Create User Account",
"PLUGIN" : "reaction rule",
"OWNER" : "rules",
"REQUIRES" : [ "civicrm", "rules" ],
"ON" : { "civicrm_entity_tag_create" : [] },
"IF" : [
  { "NOT civicrm_entity_user_exists" : { "civicrm_contact" : [ "civicrm-entity-tag:entity-id-contact" ] } },
  { "data_is" : {
      "data" : [ "civicrm-entity-tag:entity-table" ],
      "value" : "civicrm_contact"
    }
  },
  { "data_is" : { "data" : [ "civicrm-entity-tag:tag-id" ], "value" : "XXXX" } }
],
"DO" : [
  { "civicrm_entity_action_create_user" : {
      "USING" : {
        "civicrm_contact" : [ "civicrm-entity-tag:entity-id-contact" ],
        "is_active" : "1",
        "notify" : "1",
        "signin" : "1",
        "username_format" : "email"
      },
      "PROVIDE" : { "civicrm_user" : { "civicrm_user" : "Created Drupal User" } }
    }
  },
  { "redirect" : { "url" : "civicrm\/user?reset=1" } }
]


}
}

set XXX to be your Tag ID

EDIT (thx to jackrabbithanna) Make sure Entity Tag is enabled here: admin/structure/civicrm-entity/settings