It could work if you make sure that nothing rattles and the weight is approximately the same. When you just want to keep it low profile you might leave the tobacco tin with its original paint and not wrap anything around it. As some smokers put their lighters or pipe tool set in the tin even some rattling may not raise suspicion.
When police or security get the impression that you try to conceal something, they are going to give you trouble even for items you could have brought without problems. For a police officer it´s more plausible that you where too lazy to give a tin a new paint job than that you had no bad intentions when you prepared that cell phone. After all that´s what´ll count in the end.
In conclusion I´d say that even though it´s a good idea I´d not try this one.