Yes, the bots run on CS, but since CS was not a mod botman wrote his bot for, the bots don't buy weapons and don't go for the maps objectives.
You can debug these bots easily on a dedicated server, just set up MSVC accordingly (exe name: hlds.exe, parameters: the hlds launch parameters). Unfortunately with CS you can't debug them on a listen server (i.e non dedicated), because CS has code that makes the game refuse to start if it detects a debugger. If you think you are able to fool the IsDebuggerPresent() call in kernel32.dll, you will be able to use the debugger on a listen server. Get in touch with Austin from these forums, he knows how to hack the kernel32.dll
The function you will be interested in if you want to test new things in the bot is BotThink(). This is the root-level function of a bot's AI (whereas the root-level function of the
game, would be StartFrame()).
Best luck and happy hacking
P.S. btw it's not PMB's HPB_Bot, it's
botman's HPB_Bot ported to metamod. I have made NO changes to the bot code