Researching this on RealSelf, there are plenty of surgeons who are familiar with increasing the width of the pelvic area, especially those who specialize in BBL in the first place. As always, results will vary.
The important considerations are 1) having enough fat to transfer and 2) maximizing fat cell survival rates.
The first is easy enough -- in general, having a BMI of at least 23 should ensure there's enough to harvest. For the second, though, it really depends on how viable the target site is. The transferred fat cells need to establish a new blood supply to survive. The best indicator for that is having good musculature underneath the target areas. The muscles in question are the
gluteus medius, the
tensor fasciae latae, and the
iliotibial band. They can be built up using various hip abductor and glute exercises (and working the gluteus maximus certainly won't hurt, either).
The other thing that goes into the second consideration is a well-planned recovery. For the first three weeks at least, one must minimize any pressure on the target areas, while maintaining compression on the harvest areas (the harvest reduces waist size, increasing hip/waist ratio). The compression is easy, there are garments for that. The hard part is not sitting for at least three weeks, nor sleeping on your back or your sides. Most BBLs aren't as difficult because they're focused on rear projection, but for those of us who want to increase side projection, it's much more complicated. Me, I never sleep on my stomach, and I don't know I'd be able to guarantee I'd never turn over in my sleep. I'm wondering if holing up in a motel room with two beds, pulled together such that there's a gap of sufficient size for my derriere and hips to "hang out in" will do the trick. Regardless, though, the recovery will be difficult, and as with most cosmetic surgeries it takes months for bruising and swelling (and pain) to subside enough to see what the final results will be.
From my initial survey of the field, the names that I keep hearing with strong results are Dr Hughes in California and Dr Jimerson in Atlanta. There are also a lot of practices in Florida, but in Florida they're only allowed to harvest a maximum of 4L from your donor areas; in the rest of the country, the max is 5L, so I'm ruling out Florida for the time being. In general, after the purification process, about a third of the initial harvest's volume will be available for transfer.
I haven't had any consultations yet -- I'm spending the next year getting to my target weight, and working out my glutes like crazy.