Hazezon Tamar question

[serracollector]

I was playing EDH, and my opponent was playing Hazezon.  He plays it with 5 lands, during his next upkeep he gets the 5 tokens, he told me since they come at beginning of upkeep that they have haste.  Is this true?  If it is true, then why would they add haste to Icorid, if it would have haste anyways, or nether shadow etc. etc.?

[The Atog Lord]

No, something that comes into play on upkeep does not have the ability to attack that turn. If they arrived during the untap step, they could. But those upkeep-induced tokens are still sick.

[Clariax]

Even if you gain control of a creature during your untap step, it still cannot attack that turn.  (Yes, there are ways, don't need to get into that.)  A creature cannot attack unless you've controlled it continuously since the beginning of your turn.  You must already control it when your turn begins, if you gain control of it any time during the turn, regardless of how early in that turn it is, it will be unable to attack (unless it has haste, of course).

302.6. A creature's activated ability with the tap symbol or the untap symbol in its activation cost can't be activated unless the creature has been under its controller's control continuously since his or her most recent turn began. A creature can't attack unless it has been under its controller's control continuously since his or her most recent turn began. This rule is informally called the "summoning sickness" rule.