添付ビヘイビア試してみた

using System.Windows;
using System.Windows.Controls;

namespace SharpLab.IKnow.ItemBankPane {
	public class ListBoxBehavior {

		//添付されたListBoxのItemsSourceが更新された時にListBoxのスクロール位置を自動的に巻き戻すかを設定します。
		#region AutoRewind

		public static bool GetAutoRewind(ListBox listBox) {
			return (bool)listBox.GetValue(AutoRewindProperty);
		}

		public static void SetAutoRewind(
		  ListBox listBox, bool value) {
			listBox.SetValue(AutoRewindProperty, value);
		}

		public static readonly DependencyProperty AutoRewindProperty =
			DependencyProperty.RegisterAttached(
			"AutoRewind",
			typeof(bool),
			typeof(ListBoxBehavior),
			new UIPropertyMetadata(false, OnAutoRewindChanged));

		static void OnAutoRewindChanged(DependencyObject depObj, DependencyPropertyChangedEventArgs e) {
			ListBox listBox = depObj as ListBox;
			if (listBox == null)
				return;

			if (e.NewValue is bool == false)
				return;

			bool scrollToTop = (bool)e.NewValue;

			if (scrollToTop) {
				listBox.TargetUpdated += OnListBoxTargetUpdated;
			}
			else {
				listBox.TargetUpdated -= OnListBoxTargetUpdated;
			}
		}

		static void OnListBoxTargetUpdated(object sender, System.Windows.Data.DataTransferEventArgs e) {
			if (e.Property == ListBox.ItemsSourceProperty) {
				ListBox listBox = e.OriginalSource as ListBox;
				if (listBox.Items.Count > 0) {
					listBox.ScrollIntoView(listBox.Items[0]);
				}
			}
		}

		#endregion
	}
}

<ListBox v:ListBoxBehavior.AutoRewind="true" ItemsSource="{Binding NotifyOnTargetUpdated=true, Path=<適当に>}"/>