yes code for MU is included in version 1.5.2
About WP standard gallery - no.
WP uses attachments for uploaded images and I find that use external urls instead of attached images will too complex for now. I have another request about featured post image and there same problem.
But plugin has same 'gallery' from Picasa album and can create gallery from Picasa images in very manageable form. It is so glamor as gallery plugins because you see internal html :) but for me this way has more ability.
Additionally you use plugin for get the url of picasa image by some tricks:
[Code moderated as per the Forum Rules. Please use the pastebin]
this code add button to call a plugin dialog. By button click some changes happens to receive a callback after image url selected to set url to mentioned input and image inside div.
the code from live site to set special image for the post ( like featured ).