Ice tea can have alot of caffeine, almost as much as coffee, because it
is brewed quite strong usually.  It's impossible to say how much caffeine is
in a cup of tea because it varies so much.  Generally though, a Lipton
teabag will deliver around 40-50mg of caffeine in 3-5 minutes of steeping in
hot water, or steeping for several hours in cold water.    Teas made with
quality leaf (Assam, Keemun, etc.) can have up to 50-70mg of caffeine from
about 2-3 grams of tea.

 Many people say Green and Oolong tea contains less caffeine, but it really
doesn't.   Usually green and oolong tea are steep for about 1-3 minutes
(because green and oolong can become bitter with long steeping), about half
the time of black tea, so the resulting drink has less caffeine.

 One thing to do with bag teas like Lipton, which are made from fannings
and dust, is to cut the steeping time in half vs. whole leaf tea.  So you
only really need to steep it around 2-3 minutes in very hot water, because
the surface area is greater.  Loose tea, OTOH, usually takes a minute or so
just for the leaves to open up.   A bag of green tea or Oolong only needs to
steep about a minute- too long and the tea becomes bitter.

Probably as much as the same quantity of strong coffee, but if it
doesn't give you the heebie jeebies, great. I probably drink the same
but hot and strong large cups with one or two drops of saccharine
solution (?Sugarine)