Share printer across two wireless networks??

Well without a bridge between the two networks I would say no except through the internet unless you can hard wire the printer from usb to one of the macs then use the wireless print server to connect to the other network.

If you want to keep the networks separate just set up hamachi vpn on both computers. I'm sure Mac has some sort of printer sharing protocol you can use to have one computer print through the other. This sets them up to print through an SSL tunnel through the internet (might be a bit slow for photos).

Now if your going to bridge the networks I would suggest hacking your linksys routers with DD-WRT firmware and setting up a WDS bridge (sry voids warranty on router). You might also be able to bridge the two macs with the build-in airport extremes (sry not real familiar with macs but I have set up a couple of WDS bridges with airport expresses). This kind of defeats the whole purpose of having separate networks cause once bridged they would be one giant network. If you set up the routers on two different IP ranges then used hamachi to pritner share in your own network it would both work on your lan and keep the networks separate.

Personally to me this seems like way more works than just connecting over to the other network when you want to print or just connect the printer to one of the computers by usb and use the wireless print server to contact the other network.