Sorry to tell you that the profile Blurb provides isn't used for the actual printing of the books so it's highly questionable how useful if any, soft proofing with that profile becomes. You have no control over the rendering intent used at print time too, what do you setup for the soft proof? The profile is more a 'feel good' option than anything else. Each paper needs it's own profile, how can Blurb supply one? Soft proofing with a profile that isn't used to convert the data that is printed is kind of useless!
Out Of Gamut (OOG) overlays in both Photoshop and Lightroom are not accurate (a kind way of saying it's buggy). You'll see OOG overlay in images that should show none. Further. The profile (the correct profile) will handle al OOG mapping far better than we can manually. Pick the rendering intent you desire based on a good soft proof, again using the actual ICC profile based on how you prefer the rendering. Profiles know nothing about colors in context. The OOG option treats a color that's a tiny but OOG and one way out the same; with an ugly overlay. Best to ignore it. Examples of why: http://digitaldog.net/files/LR4_softproof2.mov