DISCLAIMER: Neither Arrow nor Leverage is mine. If they had been, there would have been much merging, and that many people ready to smack Oliver Queen and Nathan Ford on the nose with a rolled up newspaper.
A/N: Whoops! Now this just became a cross over! This one isn't contingent on having watched Leverage, but if you've not seen it, you should check all 5 glorious seasons out...especially if you like Arrow. Many things are the same: Robin Hood theme, Team IDs (Emotionally suppressed boss, awesome muscle who is more than just muscle, mouthy hacker), questionable decision making, WAITT fluff...
There are places on the web, the deep web, where people with their particular skill set interact, mostly for the opportunity to show off how good they are, but it's a community all the same. Friendships form in between boasting of exploits and bonding over love of other interests and hobbies. Felicity doesn't really visit too often in between her duties at work and her duty to Oliver's work, but she keeps tabs on those she has rapport with. Which is how she knows who it is that's been pinging her searches on some of the people on The List. After a brief confrontation in which both parties want to know what the other is doing-looking into dangerous men, without admitting their own reasons-they come to an understanding.
H works in a team of five to bring down the rich and powerful that have gotten so by preying on their victims: H's clients. She's familiar with the concept. Once it becomes apparent that they both hold the same role in their respective teams, working on a common goal, a deeper and more truthful connection is born. Felicity still keeps her teams' identity a secret, because duh...but suddenly it becomes a little easier to let off steam by discussing with her fellow hacker the latest technology available that's relevant to their positions. H shares the technology used to make his team's comms, always field tested by their resident muscle. Felicity's impressed enough by the schematics that she orders some from Team Arrow. She's dug up extra info for a non-Starling bad guy for H, that he wasn't able to access before. Together they re-task a satellite and find a missing child that made the national news for the Amber Alert. And amidst all that they bemoan their own woes about their teams.
H dislikes the manipulation his leader displays, Felicity sympathizes and despises the way hers punishes himself to physical exhaustion just to avoid talking about feelings. They can't share victories because that's giving too much away, but they reveal when they are victorious sometimes, if it's been a long one, or a close one, or a hard one. They both feel like the human one of the team, amongst all these other gods, so the sometimes, subtle loneliness is carried together in understanding. But they've got each other to talk to, and usually remind each other with their signature phrases:
You can always talk to me, you know.
I got you, girl. I got you.
In my perfect world where not everything hurts and Oliver only sometimes makes bad choices, I fully believe that Alec Hardison and Felicity Smoak become internet buddies and end up finding each others secret identity and helping out on open cases/jobs/whathaveyous and then completely complaining about Team drama in the down time, including insecurities. Leverage fans know that Hardison likes to peacock, but to be honest, he's a sensitive soul; much more likely to seek out advice.