No, Domain Admins do not have the rights to administrate other Domains within the forrest.
This not "out-of-the-box" behavior, at least not for the "Domain Administrators" group.
If you have a root domain of
ad.mycompany.com, and a child domain
child.ad.mycompany.com the domain admins from either domain should not be able to administer the other domain. However, the Enterprise administrators group members will be able to administrate the child domain.
However, setting up this behavior wouldn't necessarily be considered malicious if you have low role separation (E.g. Enterprise admins would be the same people as Domain Admins). Also, it wouldn't be necessary to use "not-standard utilities and hacks" as all you would need to do to allow this, is add the Domain Admin group of the parent domain to the Enterprise Admin group.
The domain admins group members in the child domain would still not have rights to administer the parent domain.