Not normally. They usually just stick to the plastic if they are purified cultures. If you infect them, they will start cluster around the infected/dead cells.
If you are doing co-cultures... the activated T cells and macrophages will tend to cluster if the stimulation is a mac processed antigen.
As for forming "tissue"... no... if you want to study a in vitro model of a 3D tissue model, that's something different.
Dear... since chemotaxis is the most important activity of Macrphages and Microphages...aggregation to each other was the most important characteristic I have noticed during my work on white blood cells response against NBT in vivo and that was confirmed in slide smears obviously.