How do you obtain intelligence on technical components of a competitor when you don't have access to it?

Even if you don't have access to the product: 

- See if you can find their product documentation online 

- Similarly, look for API documentation  

- Speak with your Sales people regularly - prospects give away tons of secrets

- Stay in touch with HR - ex-employees also have a lot of information that they ARE allowed to share and can be helpful; and when they join your company, conduct a recorded debriefing with them whenever possible 

This is tricky, and the answer may depend on the nature of your product. In B2B software, I find that there is a lot more information in the public domain today. That may include documentation, product reviews on sites like TrustRadius or G2Crowd, posts on public fora, and even job descriptions. You can get creative and stay within the bounds of competitor ethics.