Well, this may very well be a stupid answer to a stupid question
In the BRB section on magic weapons, it specifically states "Magic weapons always ignore any special rules that apply to an ordinary weapon of the same type unless otherwise specified in the description of the weapon."
I agree that regular lances should only be used when mounted (if you have to dismount for some reason, would you lug around a huge, useless lump of steel?) however, the above would suggest, that unless our lances specifically state that they can only be used while mounted (do they? i don't have my army book

), i would interpret the rules to mean they COULD be used on foot.
so, in summary, magic weapons never use anything the the BRB weapons chart, a magic weapon could be a magic sword or a magic carpet slipper, but as long as their special rules were the same, they'd do EXACTLY the same thing
Please correct me if i'm wrong
Also then, @Nicodemus, this means that BloodDrinker technichally IS a sword (as its description says so), but it follows none of the rules for normal hand weapons - it may as well be a lance, a bow or a penguin
- Vulf