In 7.x, this occurs through pcAnywhere.  After pushing or pulling the Symantec Management Agent (formerly Altiris Agent) to the Mac, enable the pcAnywhere plug-in install policy.  The pcAnywhere plug-in will be installed on the Mac and you'll be able to open a remote session.

To remote control a Mac using pcAnywhere integrated with Altiris 7:

• Actions > Remote Management > Remote Control
• Type PC  name or click Browse to select it
• Connect using: pcAnywhere
• Click Connect

As for sending scripts, this is more about remote management than remote control.  For a simple software install, like Mozilla Firefox, you'll want to download the Mac installer and then script the install.  This involves importing the installer as a software resource in the Software Library (Manage > Software; Expand Software > Software Catalog > Deliverable Software; in the right pane, click Add > Software Release) and defining the command line to use.  For example, Mozilla Firefox for us is pkg-rollout -f 'Firefox 3.6.3.dmg'.  With the software package defined, you simply assign it to a managed Mac computer (running the SMA) through a policy (check continually or send later, on a schedule) or a task (run it now).

A limitation of software deployment in Altiris 7 is that you cannot use detection rules to determine if a software resource is installed, so it's not recommended to deploy packages to Macs on a policy schedule -- you would end up installing the software again and again on top of itself.  Instead, use tasks.

There are other capabilities, too, like patching.  For a full list of what will and won't work, you'll want to visit kb.altiris.com and type in 46349 -- this is the KB number for the Support Matrix, which will have a CMS spreadsheet linked inside.  Within that you'll find a support matrix for each solution and Mac, and also a worksheet with a specific breakdown feature-by-feature.

Does this answer your question?

Note: In the documentation for the PCAnywhere solution it says the only options for authentication on the Mac agent is 'pcAnywhere' or 'OpenDirectory'. This is inaccurate wording. By 'OpenDirectory' they mean a local account on the client system, not an actual Open Directory account.
You also can't authenticate using the same credentials you log in to the SMP console with, so I suggest subscribing to KB article 52474