A few of the examples:

:: Central Park (NYC) - image via The Infrastructurist

:: The Tiergarten (Berlin) - image via The Infrastructurist

:: Hyde Park (London) - image via The Infrastructurist
"The stainless steel solar loo would prove economical on maintenance and is functional in all climate with solar powered lighting, heaters and ventilation. In my opinion, the other cities should try the product as it is eco-friendly and would save a lot of money both in the production and usage departments."
While full scale toilets are an option, these often lead to potential crime issues (or opportunities for policing) and in the case of Seattle, a total and expensive removal after a rash of issues. Perhaps a more simple and decentralized type of facility is necessary.
A couple of examples. The first, via Treehugger, offers a sculptural option of the 'Pee Tree' by Joa Herrenknecht, which: "...has the abstracted form and the dimensions of a tree. It's bright ceramic white is a strong signal and is to be seen from far - making it accessible when in urgent need. The trunk offers a perfect place for messaging, e.g. the common "I was here" or "done that" statements, which we all know from Club-toilets."
:: image via Treehugger
A more small-scale example (via the Design Blog) is the Axixa by Mexican designer Miguel Melgarejo, who: "...has come up with a public urinal concept... that will help in maintaining the cleanliness in the streets. Featuring the shape that a leak leaves on a wall, the public ceramic urinal generates a permanent mark in public streets or places where people can urinate and participate in a manifestation in which the disposal itself becomes part of the public life."