@ckrapu - wow, thanks for the pointer. I just went through the MULTIBUG document and found that it is not sd but tau. you are absolutely correct and thanks for jumping and being a savior.
In the BUGS language it is used as
x ~ dnorm(mu, tau)
@cluhmann - I am sorry, I got confused and thought this is R code where as it is Multibug specific code. I came to know after running the example in MULTIBUG IDE(Tutorial)
As soon as I changed my code to below in pymc3, I can see value approximately matching to the result in MULTIBUGS.
alpha_0 = pm.Normal(‘alpha_0’, mu=0., tau=1e-6)
Let me try few things and might seek some help.