[...]
# Enable mouse mode
set -g mode-mouse on
set -g mouse-resize-pane on
set -g mouse-select-pane on
set -g mouse-select-window on

# Mouse pane switching
set-option -g mouse-select-pane on
[...]

alias tcs="tmux -f ~/.tmux.conf.iterm -CC new -s"
alias tca="tmux -f ~/.tmux.conf.iterm -CC attach -t"