Strategy wise the player side should just assign the bugs and Phoenix Hawk (and possibly the Chameleon) as the "survivor" force and run/jump like hell. The bugs have poor pilots and will get murdered if the clan force gets LOS and the Chameleon and Pixie are both heat constrained. The other mechs won't be able to get away anyway.
The clan forces has seven jumpers: the Viper, Kit Fox S, Summoner, Conjurer, Executioner, Hunchback IIC, and Nova. The Viper can jump 8, which will be a problem. The Kit Fox and Conjurer are fast enough to pace the bugs with 6 jump, followed by the Nova and Summoner at 5 Jump and the rounded out by the Executioner and Hunchback IIC at 4 jump. They can be dispatched as a hunter killer formation to ensure that the allied units don't escape.
The Heavy urban terrain will help the PCs and offer opportunities to inflict damage, particularly on the Kit Foxes. The Hellbringer and Vulture will be reasonable targets with their relatively lighter armor. The Summoner also falls into that category but will probably have a higher mod due to jumping. The Hunchback is definitely vulnerable due to its light armor, but... The Executioner is just a zone of death with 3 large pulse lasers and 4 ER mediums as well as the armor to ensure it can use them and the heatsinks to do it often. Interestingly, the Executioner's side torso armor is weak and it has left torso MG ammo. So it is semi-vulnerable to attack.