Are new blood vessels able to deliver oxygen to hypoxic tissue before the establishment of blood circulation?
It is true that for long-term oxygen delivery the new vasculature must establish circulation. However, when the new vessels are starting to maturate they are filled with blood coming from the main vessel, which carries oxygen.

Since the endothelial cells of the new vessel derive most of their energy anaerobically through glycolysis (Quintero et al, 2006; Dagher et al, 2001; Krutzfeldt et al, 1990; Peter Fraisl et al, 2009), a metabolic mechanism  activated in critical microenvironments like hypoxic tissue (DeBerardinis et al, 2008), the oxygen in the lumen is free to be immediately delivered to the tissue. 

Thus it is fair to assume that  at least for a short period of time the cells near to the new vessel are being oxygenated.



References:

Quintero, M., Colombo, S.L., Godfrey, A., and Moncada, S. (2006). Mitochondria as signaling organelles in the vascular endothelium. Proc. Natl. Acad. Sci. USA 103, 5379–5384.              

Dagher, Z., Ruderman, N., Tornheim, K., and Ido, Y. (2001). Acute regulation of fatty acid oxidation and amp-activated protein kinase in human umbilical vein endothelial cells. Circ. Res. 88, 1276–1282.                                                      

Krutzfeldt, A., Spahr, R., Mertens, S., Siegmund, B., and Piper, H.M. (1990). Metabolism of exogenous substrates by coronary endothelial cells in culture. J. Mol. Cell. Cardiol. 22, 1393–1404. 

DeBerardinis, R.J., Lum, J.J., Hatzivassiliou, G., and Thompson, C.B. (2008). The biology of cancer: metabolic reprogramming fuels cell growth and prolif- eration. Cell Metab. 7, 11–20.