if you want extended game data then your better off just getting it through a hook (bot or mm) like I did for the hl web tv deal.
As PM stated I believe to get hltv info you must connect and auth as a valid hltv client. The client does send data back to indicate which player to watch or to use the topographical mode (whatever its called). You might be able to hi-jack the hltv messages in a mm plugin but you would prolly need a hltv client connected or the info might not exist (engine only sends if a hltv client is connected ???). I dunno, sub to the
hlcoders@list.valvesoftware.com mailing list and ask around...