Hi i am kinda new here but is a LP summit event like a paid meet and greet ?
A summit is where the band takes you back stage, shows you around, you get to go on stage and play with there instruments, you get to stay for there soundcheck. its better than a meet and greet if you ask me , but i dont think you can get things signed, but im not sure.
You get to meet the band, and get one item signed. 
There’s also auctions, Q&A with the band, etc.
“Although each Summit’s activities vary, fans have historically gotten to meet the band, watch sound checks and intimate acoustic performances, take pictures on the band’s stage with their instruments, work on Music For Relief charity events, tour the crew bus and backstage, and more. Summit events are by invitation only.”
Video of the summit in London: http://www.linkinpark.com/video/international-lpu-summit-in